ACUS01 KWNS 141938
SWODY1
SPC AC 141937

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0137 PM CST Thu Jan 14 2021

Valid 142000Z - 151200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast through tonight.

...20z Update...

Thunderstorms are not expected through the remainder of the period
and no changes are needed with this update.

..Leitman.. 01/14/2021

.PREV DISCUSSION... /ISSUED 0949 AM CST Thu Jan 14 2021/

...1630z Update...

No changes to earlier thoughts regarding the convective potential
across the contiguous United States.

$$
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ACUS01 KWNS 151940
SWODY1
SPC AC 151939

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0139 PM CST Fri Jan 15 2021

Valid 152000Z - 161200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
A few brief thunderstorms are possible over the middle Ohio Valley
to Cumberland Plateau this afternoon.

...20z Update...

The ongoing forecast remains on track and no changes have been made
with this update.

..Leitman.. 01/15/2021

.PREV DISCUSSION... /ISSUED 1025 AM CST Fri Jan 15 2021/

...Lower/Middle Ohio Valley to Cumberland Plateau...
Cold mid-level temperatures (low to mid -30s C at 500mb) associated
with the Midwest-centered cyclone will overspread the region through
tonight. Relatively cloud-free skies over the Lower/Middle Ohio
Valley and Cumberland Plateau will contribute to a further
steepening of low/mid-level lapse rates this afternoon. Even while mixing/low-level drying will tend to occur, a warming boundary layer
with scant moisture/buoyancy may be sufficient for a few low-topped thunderstorms this afternoon.

$$
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ACUS01 KWNS 161630
SWODY1
SPC AC 161629

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1029 AM CST Sat Jan 16 2021

Valid 161630Z - 171200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Very isolated lightning flashes may occur along the New England
coast this afternoon.

...New England...
Bands of semi-organized low-topped convection ongoing near Cape Cod
at midday will transition north-northeastward toward coastal Maine
through the afternoon. While the highest probability of
thunderstorms will remain well offshore, marginally supportive
thermodynamic profiles near the coast could support a few lightning
flashes this afternoon.

...Central Appalachians/Mid-Atlantic States...
Although cloud cover will tend to remain prevalent, modest boundary-
layer heating beneath the upper trough-related mid-level cold core
(-30C to -35C at 500 mb) will yield steepening lapse rates. A few
lightning flashes cannot be entirely ruled out this afternoon, but
the potential/coverage is expected to remain very low overall (less
than 10 percent).

..Guyer/Leitman.. 01/16/2021

$$
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ACUS01 KWNS 161948
SWODY1
SPC AC 161946

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0146 PM CST Sat Jan 16 2021

Valid 162000Z - 171200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not expected across the U.S. mainland the rest of
today or tonight.

...Discussion...

An expansive area of rain and snow will persist this afternoon along
the warm conveyor belt and just ahead of a vorticity maximum lifting
northward through Maine. However, instability appears too marginal
to support thunderstorms.

A few lightning flashes cannot be completely ruled out this
afternoon with showers developing beneath the cold core of an upper
low circulation from the central and southern Appalachians into the
Middle Atlantic region. However, it still appears that coverage of
any such activity will remain less than 10%.

..Dial.. 01/16/2021

.PREV DISCUSSION... /ISSUED 1029 AM CST Sat Jan 16 2021/

...New England...
Bands of semi-organized low-topped convection ongoing near Cape Cod
at midday will transition north-northeastward toward coastal Maine
through the afternoon. While the highest probability of
thunderstorms will remain well offshore, marginally supportive
thermodynamic profiles near the coast could support a few lightning
flashes this afternoon.

...Central Appalachians/Mid-Atlantic States...
Although cloud cover will tend to remain prevalent, modest boundary-
layer heating beneath the upper trough-related mid-level cold core
(-30C to -35C at 500 mb) will yield steepening lapse rates. A few
lightning flashes cannot be entirely ruled out this afternoon, but
the potential/coverage is expected to remain very low overall (less
than 10 percent).

$$
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ACUS01 KWNS 171135
SWODY1
SPC AC 171134

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0534 AM CST Sun Jan 17 2021

Valid 171300Z - 181200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not expected across the contiguous U.S. through
tonight as environmental conditions remain unsuitable.


..Grams.. 01/17/2021

$$
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ACUS01 KWNS 171928
SWODY1
SPC AC 171927

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0127 PM CST Sun Jan 17 2021

Valid 172000Z - 181200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not expected across the contiguous U.S. through
tonight.

...Discussion...

The previous forecast remains on track. Rain and snow showers will
persist across the OH Valley and central Appalachians this afternoon
and evening, but the depth of the convective layer and degree of
instability are too marginal for thunderstorms.

..Dial.. 01/17/2021

.PREV DISCUSSION... /ISSUED 1030 AM CST Sun Jan 17 2021/

...Synopsis/Discussion...
The potential for lightning-producing convection will be essentially
nil across the CONUS this afternoon and tonight. Associated with an
advancing shortwave trough, a couple of lightning flashes cannot be conclusively ruled out this afternoon amid steep lapse rates across
the middle Ohio Valley and Cumberland Plateau, however this
potential should remain very low given the very shallow nature of
the convection.

$$
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ACUS01 KWNS 181630
SWODY1
SPC AC 181628

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1028 AM CST Mon Jan 18 2021

Valid 181630Z - 191200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated non-severe thunderstorms are possible late tonight into
early morning Tuesday across a portion of central to east Texas.

...Central/east Texas...
Scattered showers are expected to develop/increase late tonight
through the early morning hours of Tuesday near/behind the surface
reflection of a southeastward-advancing cold front. Minimal elevated
buoyancy through a sufficient depth may allow for charge separation
and some lightning flashes in the pre-dawn hours of Tuesday.

..Guyer.. 01/18/2021

$$
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ACUS01 KWNS 182002
SWODY1
SPC AC 182000

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0200 PM CST Mon Jan 18 2021

Valid 182000Z - 191200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not expected across the U.S. mainland the rest of
today or tonight.

...Eastern Texas...

Modified continental polar air with 50s to around 60 F dewpoints
will advect through eastern TX ahead of a southward-advancing cold
front, resulting in a shallow unstable layer above the surface.
Scattered elevated showers are likely within the frontal zone as
well as the warm sector late tonight. However, it appears the
convective layer will not deepen sufficiently to support a 10% or
greater coverage of thunderstorms prior to 12Z.

..Dial.. 01/18/2021

.PREV DISCUSSION... /ISSUED 1028 AM CST Mon Jan 18 2021/

...Central/east Texas...
Scattered showers are expected to develop/increase late tonight
through the early morning hours of Tuesday near/behind the surface
reflection of a southeastward-advancing cold front. Minimal elevated
buoyancy through a sufficient depth may allow for charge separation
and some lightning flashes in the pre-dawn hours of Tuesday.

$$
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ACUS01 KWNS 201942
SWODY1
SPC AC 201940

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0140 PM CST Wed Jan 20 2021

Valid 202000Z - 211200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated non-severe thunderstorms are possible across the Lower
Colorado Valley and southern Arizona through tonight.

...20z Update...

The ongoing forecast remains on track, and no changes are necessary
with this update. For forecast details, please see the previous
discussion below.

..Leitman.. 01/20/2021

.PREV DISCUSSION... /ISSUED 1029 AM CST Wed Jan 20 2021/

...Southern Arizona/far southeast California...
A closed upper low west of the Baja Peninsula will become somewhat
more progressive as it evolves into an open wave through early
Thursday morning while approaching the northern Gulf of California.
Preceding it, a plume of sufficient low to mid-level moisture across
the peninsula and gulf will support periods of showers and embedded thunderstorms mostly across the northwest portions of Mexico and
adjacent waters. Some of this activity will spread across the
international border, mainly later this afternoon through tonight
across southern Arizona. Severe thunderstorms are unlikely owing to
meager buoyancy and weak low-level winds.

$$
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ACUS01 KWNS 211948
SWODY1
SPC AC 211946

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0146 PM CST Thu Jan 21 2021

Valid 212000Z - 221200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Although severe thunderstorms are not expected, thunderstorms will
continue across parts of southern Arizona through early evening, and
from eastern Texas into the lower Mississippi Valley tonight.

...20z Update...

Only minor changes have been made to the 10% General Thunder line
across southern AZ. General thunder has been removed across
southwest AZ as the upper trough continues to eject eastward.
Isolated thunderstorms have been noted near the U.S./Mexico border
this afternoon, and this activity may continue for several more
hours.

Otherwise, the remainder of the previous outlook remains unchanged,
with additional isolated thunderstorms possible from eastern TX into
the lower MS Valley tonight.

..Leitman.. 01/21/2021

.PREV DISCUSSION... /ISSUED 1029 AM CST Thu Jan 21 2021/

...Southern Arizona...
In relation to the eastward-ejecting/de-amplifying shortwave trough
over northwest Mexico, a few thunderstorms will remain a possibility
mainly across far southern portions of Arizona through the
afternoon.

...East Texas into lower Mississippi Valley...
Additional moistening/lift in vicinity of a west/east-oriented
low-level baroclinic zone may become conducive for some
thunderstorms this evening into the overnight.

...Coastal areas of southern Oregon/northern California...
In association with a southward-digging shortwave trough, convection
should increase late tonight beneath the mid-level cold core. A few
lightning flashes could occur offshore, but the near-shore/coastal
thunderstorm potential should remain very low (less than 10
percent).

$$
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ACUS01 KWNS 221935
SWODY1
SPC AC 221933

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0133 PM CST Fri Jan 22 2021

Valid 222000Z - 231200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
No severe weather is expected across the U.S. today and tonight.

...20z Update...

Minor changes have been made to the 10% General Thunder area in
central CA. The thunder area has been trimmed on the northern and
eastern edges to account for latest model and observational trends.
A few lightning flashes are still possible near the Bay Area
southward toward San Luis Obispo County. Otherwise, the ongoing
forecast remains on track.

..Leitman.. 01/22/2021

.PREV DISCUSSION... /ISSUED 1022 AM CST Fri Jan 22 2021/

...CA/NV/UT/AZ...
A compact upper low and associated strong shortwave trough will
pivot from the central CA coast into southern NV through tonight. A
pocket of cold temperatures aloft and steep lapse rates will
accompany this system, promoting convective showers and isolated
thunderstorms. No severe storms are anticipated, although small
hail is possible in the more intense showers.

$$
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ACUS01 KWNS 231251
SWODY1
SPC AC 231250

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0650 AM CST Sat Jan 23 2021

Valid 231300Z - 241200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
A few non-severe thunderstorms may develop across parts of southern
California near the coast today, and late overnight over northern
Louisiana.

...Synopsis/Discussion...
A complex, mid/upper-level cyclone -- now covering parts of the
Great Basin westward to coastal north-central CA -- is expected to
consolidate in favor of its western lobe through the period. This
will occur as an eastern vorticity max and original cyclone center
-- now apparent on moisture-channel imagery over central NV --
ejects northeastward to the central Rockies, and weakens in
confluent flow. Meanwhile, the western portion of the gyre contains
vorticity maxima over inland northern CA and southwest of MRY.
Those will phase enough to form a new, dominant cyclone moving
southeastward down the southern CA coast through this evening. The
new cyclone and attendant trough should pivot eastward across
southern CA to near the lower Colorado River Valley and northern
Baja between 06-12Z.

At the surface, mostly cool to cold and stable conditions prevail
across the interior CONUS from the Rockies to the East Coast. A wavy/quasistationary frontal zone was drawn at 11Z from central FL
across the northern Gulf, bending southwestward/southward off the
lower TX Coast.

...Southern CA to southern AZ...
Midlevel cooling and related steepening of low/middle-level lapse
rates will occur atop a moist marine layer, as the cyclone develops
and approaches. This should result in sufficiently deep buoyancy to
extend at least locally/briefly through a rising inversion and into
icing layers suitable for lightning production near the coast.
Forecast soundings suggest 100-300 J/kg MUCAPE, with similar MLCAPE
over water and immediate coastal areas as the cyclonic cold core
moves nearby. Farther east, an area of widely scattered to
scattered showers may develop over northwestern MX and the northern
Gulf of CA tonight, moving/spreading north-northeastward over parts
of southern AZ. Although forecast soundings suggest CAPE will
remain too shallow for an areal thunderstorm threat north of the
international border, very isolated lightning cannot be ruled out.

...Northern LA and vicinity late tonight...
A few thunderstorms are possible within the last few hours of the
period -- roughly 09-12Z -- embedded within a growing area of precip
rooted in an elevated inflow layer. A broad area of low-level warm
advection and isentropic lift will continue to expand and strengthen
through the period over the western Gulf States, beneath broadly
anticyclonic mid/upper flow and north of the surface baroclinic zone
over the Gulf. Though forcing aloft will be minimal, gradual
moistening within the warm advection plume is expected above a
relatively stable boundary layer. The increase in theta-e from
about 800-900 mb results in MUCAPE 300-800 J/kg off the east rim of
the EML after about 09Z, with isentropic lift to an LFC. Modest
lapse rates and lack of buoyancy should preclude a severe threat.

..Edwards.. 01/23/2021

$$
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ACUS01 KWNS 231930
SWODY1
SPC AC 231929

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0129 PM CST Sat Jan 23 2021

Valid 232000Z - 241200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
A few thunderstorms may develop across parts of southern California
near the coast today, and late overnight over northern Louisiana. No
severe storms are expected.

...20Z Update...
Prevailing forecast remains valid with no changes needed.

..Mosier.. 01/23/2021

.PREV DISCUSSION... /ISSUED 1013 AM CST Sat Jan 23 2021/

No changes have been made to the ongoing forecast. Satellite
imagery continues to show scattered showers off the coast of
southern CA near a mid-level cold pocket. This activity may spread
inland this afternoon, with a few thunderstorms possible over the LA
Basin. Other elevated showers and thunderstorms may affect parts of
LA late tonight (mainly after 09z) in an developing low-level warm
advection regime. No severe storms are expected.

$$
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ACUS01 KWNS 241251
SWODY1
SPC AC 241250

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0650 AM CST Sun Jan 24 2021

Valid 241300Z - 251200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF NORTH-CENTRAL/NORTHEAST TEXAS AND SOUTH-CENTRAL/SOUTHEASTERN
OKLAHOMA...

...SUMMARY...
Large hail and isolated wind damage will be possible this evening
and tonight across parts of the southern Plains.

...Synopsis...
In mid/upper levels, a pronounced split-flow pattern exists over the
western CONUS, with the splitting feature being a cyclone over
southern CA and trough extending southwestward from there. Upstream
troughing -- extending south-southeastward from a cyclone over the
gulf of Alaska -- will dig southeastward toward and across the CONUS
Pacific Coast today and tonight. As that occurs, the leading
cyclone will pivot eastward and devolve to a strong open shortwave
trough over AZ and Sonora by 00Z. The trough will deamplify further
-- but remain well-defined -- as it ejects northeastward across NM
and the south-central High Plains by 12Z tomorrow.

At the surface, 11Z analysis showed a cold front from the upper
Mississippi Valley across southeastern KS, through a weak low near
PNC, then southwestward over southern NM. A dryline was drawn from southwestern OK/northwest TX through a weak low near FST, then
southeastward over northern/central Coahuila. A separate, marine
warm-frontal zone was evident across the northern Gulf shelf waters
westward over deep south TX. The TX part of this boundary will
diffuse as it shifts northward today, with another warm frontal zone
developing over north-central/northeast TX this evening, on the
southern fringe of a large area of precip and embedded convection.
The cold front will overtake the dryline from north-south through
the period, as 60s F surface dew points spread northward in the warm
sector. The southwest TX surface low should ripple northeastward
along the cold front from 00Z onward, approaching the SPS area by
06Z and moving between TUL-FSM around 12Z. By then, the cold front
should extend from the low across southeastern OK and northeast
through south-central TX.

...Southern Plains to AR...
Scattered to locally numerous thunderstorms are possible within two
main episodes:
1. A broad area of convection forming along and mostly north of the
warm front and surface low this afternoon and evening, spreading/
expanding northeastward across much of north-central/northeast TX,
the Red River region, central/eastern OK, and into portions of AR
and the Ozarks tonight.
2. Thunderstorms developing initially over parts of northwest TX
this evening (probably after 00Z) and moving northeastward, while expanding/backbuilding. The net effect should be a growing area of increasingly organized thunderstorms shifting eastward over north TX
and southern OK overnight, ultimately merging with the northwestern
part of the first regime over eastern OK or AR.

Large hail will be possible in both regimes, with elevated
supercells possible in the first. The second may access enough
MUCAPE (up to 1000-1500 J/kg) and greater effective-shear magnitudes
(55-70 kt) to support both supercell and bowing structures. While a
strong and fairly deep stable layer will persist across most of OK,
sufficient buoyancy and downdraft intensity may develop above that,
in an organized convective complex, to penetrate isolated severe
gusts to the surface.

An antecedent EML is in place over much of central/south TX,
well-sampled by 12Z RAOBs from CRP/BRO/DRT. The EML will spread
northward and northeastward, weakening north of the surface warm
front, and will remain viable long enough to substantially limit or
even prevent development in the free warm sector (south of the warm
front). Direct upper-level support from the ejecting trough will be
limited as well, at best glancing the northwest fringes of the warm
sector. The strongest large-scale ascent (and great majority of
substantial convection) should be in a plume of buoyancy elevated
over relatively stable surface conditions farther poleward.

Nonetheless, strong low-level lift will be associated with the
segment of the cold front near and just south of the progressive
surface low, as the boundary impinges on the northern part of the
warm sector late tonight. This should overcome the basal EML
inversion and encourage convective initiation within about 50 kt effective-shear magnitudes, and at least some access to relatively
high theta-e in the warm sector, across parts of north-central/
central TX. The DFW Metroplex already was included in the area of
largest outlook probabilities for its portion of this regime.
However, more room is being given farther south for potential
backbuilding of thunderstorms, and at least marginal severe
potential therewith.

..Edwards/Gleason.. 01/24/2021

$$
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ACUS01 KWNS 241947
SWODY1
SPC AC 241945

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0145 PM CST Sun Jan 24 2021

Valid 242000Z - 251200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
NORTH TEXAS AND SOUTHERN OKLAHOMA...

...SUMMARY...
Large hail and isolated wind damage will be possible this evening
and tonight across parts of the southern Plains.

...20Z Update...

...Southern Plains into the Ozark Plateau...
Recent surface analysis places a frontal low near SPS, with the cold
front extending northeastward to another low in northeast OK and
southwestward into the Permian Basin. A shortwave trough remains
well west of the region over the Lower CO River, keeping warm-air
advection as the primary forcing for ascent. A few storm clusters
have developed with in this regime with several deeper updrafts
noted over northwest TX and central TX.

With the cold front forecast to continue gradually southeastward,
any afternoon/evening storms will occur north of the front.
Expectation is for overall coverage to increase this evening across
OK and AR as the low-level jet increases. As mentioned in the
previous outlook, combination of modest elevated buoyancy and strong
vertical shear will result in the potential for hail through the
evening.

As the shortwave through and its attendant forcing move closer
tonight, storm coverage will likely increase from west TX across OK
and into northern AR. Hail will remain the primary threat with these
storms. A relatively small corridor of surface-based storms may
develop along and just ahead the front from far south-central OK
into north-central TX early Monday morning, continuing east just
ahead of the front thereafter.

..Mosier.. 01/24/2021

.PREV DISCUSSION... /ISSUED 1014 AM CST Sun Jan 24 2021/

...Southern Plains...
Only minor changes have been made to the ongoing outlook. An upper
low currently over far southern CA will develop into a progressive
shortwave trough and rotate across NM/west TX later tonight. This
will result in surface cyclogenesis and strengthening low-level
winds over east TX. Enhanced low-level warm advection across parts
of the region will lead to a few thunderstorms this
afternoon/evening, with more widespread deep convection tonight as
the primary forcing and lift overspreads the area.

Present indications are that afternoon showers and a few
thunderstorms will affect northeast TX/southeast OK into adjacent
parts of LA/AR. These storms will be mainly elevated to the north
of the surface warm front, where weak CAPE may support hail in the
strongest cores. The risk of severe storms appears marginal.

After dark, more organized thunderstorms will develop over parts of
west TX/southwest OK as the primary forcing arrives, and in the warm
sector across north TX/southeast OK as better low-level moisture
becomes established. These storms will likely be more intense, with
hail and gusty winds possible. Activity will likely persist through
the night, spreading northeastward into parts of AR and southern MO.

$$
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ACUS01 KWNS 161630
SWODY1
SPC AC 161628

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1028 AM CST Tue Feb 16 2021

Valid 161630Z - 171200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
The risk for organized severe thunderstorms appears negligible
through tonight.

...Southeast FL...
As advertised in the prior outlook, low-level winds have weakened
and veered per recent AMX VWP data with a pronounced weakness in
mid-level flow around 500 mb. This suggests the risk for additional
supercells will remain negligible. Some uptick in thunderstorm
coverage should occur this afternoon as the arctic front settles
south before stalling. Potential will exist for small hail in the
deepest updrafts given moderate buoyancy and moderate speed shear
from 400 to 250 mb. Hail-laden downdrafts may aid in a few
microbursts capable of strong wind gusts.

..Grams.. 02/16/2021

$$
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ACUS01 KWNS 171951
SWODY1
SPC AC 171949

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0149 PM CST Wed Feb 17 2021

Valid 172000Z - 181200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE CENTRAL GULF COAST THROUGH TONIGHT...

...SUMMARY...
Isolated to scattered damaging winds and a couple tornadoes are
possible across a portion of the central Gulf Coast, after about 6
PM CST through the overnight.

...20z Update - Central Gulf Coast...

The main changes with this update are to pull the Marginal risk
southward across MS/AL/GA. Latest guidance suggests the surface warm
front will hug the immediate coastal area from near the mouth of the
MS River to near Mobile and the FL Panhandle. As a result, most
convection will remain elevated and over a much cooler airmass
across southern MS/AL and southwest GA. Instability will remain
limited, but strong effective shear will result in some organized
convection moving inland from the Gulf. In the vicinity of the
surface warm front, low level SRH will be maximized, and the
greatest threat for damaging gusts or a couple of tornadoes will be
along the frontal zone. As a result, the Slight risk area remains
unchanged from the previous outlook.

..Leitman.. 02/17/2021

.PREV DISCUSSION... /ISSUED 1028 AM CST Wed Feb 17 2021/

...Central Gulf Coast...
No change has occurred with the cat 1 and 2 (MRGL and SLGT) risk
areas. Primary mitigating concern for expansion or greater
probabilities is the extent of surface-based warm sector inland
within a very tight baroclinic zone.

Surface cyclone over the northwest Gulf is progged to gradually fill
as it approaches the western FL Panhandle through late tonight.
Thunderstorms are expected to initially develop near this cyclone
and then expand in coverage during late afternoon into tonight,
primarily from elevated parcels north of the warm front. Initial
linear organization for severe potential will probably commence just
offshore of the south-central LA coast by late afternoon. This
activity should eventually overlap with the impinging of low to mid
60s surface dew points into a portion of southeast LA during the
evening. Here, rather enlarged low-level hodographs coincident with
50-60 kt effective shear should yield potential for embedded
supercell structures within the squall line, capable of producing a
few tornadoes and damaging winds.

The very tight baroclinic zone will be characterized by an
increasingly sharp low-level inversion with northern extent likely
limiting the areal coverage of tornado and damaging wind potential
farther inland (this region recently warming above freezing as of
16Z). Given the strength of the flow aloft, it is plausible that
line segments may spread quickly northeast and outpace the
surface-based warm-sector before it reaches the FL Panhandle
overnight. The eastern portion of the tornado/wind risk (near the
central portion of the FL Panhandle) between about 09-12Z may
emanate from convection that can form in pre-frontal confluence
bands across the northeast Gulf.

$$
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ACUS01 KWNS 181631
SWODY1
SPC AC 181630

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1030 AM CST Thu Feb 18 2021

Valid 181630Z - 191200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FLORIDA PANHANDLE
TO SOUTH GEORGIA...

...SUMMARY...
A couple tornadoes and locally damaging winds are possible through
mid-evening across the Florida Panhandle and south Georgia.

...FL Panhandle to south GA...
Categorical risk areas have been mainly adjusted to decrease the
western and northern extent with a persistent, low probability
tornado environment expected to continue into this evening.

Overall lightning trends have decreased somewhat through late
morning within a swath of scattered convection that is elevated from
the eastern Carolinas to surface-based over the northeast Gulf. The
surface warm sector characterized by mid to upper 60s surface dew
points resides across the central to eastern Panhandle and north FL
into a portion of south-central to southeast GA. A lack of stratus
in north FL to southeast GA will result in more robust
boundary-layer heating and the front reaching the Savannah to
southwest GA vicinity before oscillating back south later today.
This heating will likely be necessary to aid in sustaining
surface-based thunderstorm redevelopment given the weak mid-level
lapse rates evident in 12Z observed soundings across FL.

Low-level southwesterlies should be strongest at present and slowly
subside into this evening, but at least 40 kt flow will likely
persist through late afternoon. With a lack of cyclogenesis,
low-level hodographs, while adequate for supercell development, are
unlikely to broadly improve. This suggests the severe threat may
remain conditional, and require convection to develop/spread towards
the warmer boundary layer farther east. A weakening trend should
ensue after sunset as the boundary layer cools and low-level
hodographs become increasingly marginal.

..Grams/Bentley.. 02/18/2021

$$
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ACUS01 KWNS 191956
SWODY1
SPC AC 191954

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0154 PM CST Fri Feb 19 2021

Valid 192000Z - 201200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
A strong storm or two with gusty winds remains possible this
afternoon. However, a sustained, organized severe event is not
expected.

...Southern Florida Peninsula...

A few thunderstorms continue developing along and south of a cold
front moving through the southern half of the Florida Peninsula. A
strong storm or two remains possible this afternoon, especially near
the east coast. However, a marginal thermodynamic environment with
very weak mid-level lapse rates will preclude an organized severe
event.

..Dial.. 02/19/2021

.PREV DISCUSSION... /ISSUED 1021 AM CST Fri Feb 19 2021/

...Discussion...
A progressive upper flow pattern will continue across the U.S.
today, as one trough shifts across eastern portions of the country
and a second moves onshore over the West, during the overnight
portion of the period.

At the surface, cold high pressure will continue to prevail east of
the Rockies, with a cold front -- at the leading edge of the polar
airmass -- moves steadily southward across the Florida Peninsula.

A band of showers -- with a couple of embedded lightning flashes --
is accompanying the southward progression of the front across
Florida. While low 70s surface dewpoints characterize the
pre-frontal airmass which -- combined with ongoing daytime heating
-- are contributing to 500 to 1500 J/kg mixed-layer CAPE, weak lapse
rates aloft will continue to hinder more appreciable
destabilization. Additional, moderate/unidirectional flow aloft --
roughly aligned with the surface front -- is also not particularly
favorable for well-organized convection. While a couple of stronger
storms could produce gusty winds through this afternoon, any severe
risk remains too low to warrant inclusion of any risk areas.

Elsewhere, a few lightning flashes may occur late in the period,
near the northern California coast as the aforementioned upper
trough crosses the area overnight.

$$
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ACUS01 KWNS 200522
SWODY1
SPC AC 200521

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1121 PM CST Fri Feb 19 2021

Valid 201200Z - 211200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
A few thunderstorms will be possible across a portion of the Great
Basin this afternoon.

...Synopsis...
Surface high pressure will promote cool, dry low-level conditions
across much of the central and eastern CONUS, limiting deep moist
convective potential. Across the Interior West though, a mid-level
trough will traverse the area while amplifying. Cold 700-500 mb
temperatures accompanying the approaching trough will result in
steep (8-9 C/km) mid-level lapse rates, fostering enough buoyancy in
the -10 to 30C layer to support some charge separation in any
convective updrafts that develop. Deep-layer ascent ahead of the
trough axis may help mechanically lift low-level parcels to the
-10-30C layer, with a couple of thunderstorms possible, mainly
during the afternoon hours.

..Squitieri.. 02/20/2021

$$
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ACUS01 KWNS 201926
SWODY1
SPC AC 201925

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0125 PM CST Sat Feb 20 2021

Valid 202000Z - 211200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms are possible across a portion of the Great
Basin this afternoon.

...20Z Update...
A few lightning strikes are still possible ahead of the shortwave
trough moving through the Great Basin. No lightning is expected
elsewhere across the CONUS.

..Mosier.. 02/20/2021

.PREV DISCUSSION... /ISSUED 1006 AM CST Sat Feb 20 2021/

...Great Basin this afternoon...
No changes to previous outlook. A midlevel shortwave trough and an
associated baroclinic zone will move over NV/UT this afternoon, and
reach the Four Corners tonight. Steep low-midlevel lapse rates will
allow weak surface-based buoyancy to develop this afternoon, and
some low-topped convection is expected in the zone of ascent along
the baroclinic zone. Relatively cool profiles will tend to limit
buoyancy and suggest that most of the precipitation will fall as
snow. It appears that the somewhat greater threat for isolated
lightning flashes will be this afternoon when the low levels are
warmest.

$$
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ACUS01 KWNS 210529
SWODY1
SPC AC 210528

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1128 PM CST Sat Feb 20 2021

Valid 211200Z - 221200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized thunderstorms are not expected across the continental U.S
today.

...Synopsis...
A positively tilted mid-level trough will track across the central
U.S through the period. Ahead of the trough axis, strong westerly
flow aloft is expected to overspread the Ohio and Tennessee Valleys, particularly by late afternoon into the overnight hours. Strong
forcing for ascent will promote the development of widespread rain
showers ahead of a cold front while a surface low drifts towards the
Great Lakes. Despite strong, deep-layer flow fields and lift ahead
of the cold front, buoyancy is expected to be absent across the
Ohio/Tennessee Valleys given poor low-level airmass recovery in the
warm sector and mediocre tropospheric lapse rates. While showers may
promote occasionally gusty conditions, thunderstorm development
appears unlikely, with no general thunder areas delineated. Across
the western U.S, widespread surface high pressure and cool/dry
conditions are expected to mitigate thunderstorm development.

..Squitieri.. 02/21/2021

$$
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ACUS01 KWNS 211936
SWODY1
SPC AC 211935

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0135 PM CST Sun Feb 21 2021

Valid 212000Z - 221200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not expected across the continental U.S. through
tonight.

...20Z Update...
No changes needed to the previous forecast.

..Mosier.. 02/21/2021

.PREV DISCUSSION... /ISSUED 1015 AM CST Sun Feb 21 2021/

...Synopsis...
A positive-tilt midlevel shortwave trough will move eastward over
northern MO and IA today, and the OH Valley tonight. Lingering
steep lapse rates above the 700 mb level will support some midlevel
convective elements, where ascent is focused by low-level warm
advection and within the left-exit region of the mid-upper jet over
IA. However, profiles will likely remain too cold for any
appreciable threat for lightning flashes. Otherwise, a modifying
air mass will spread northward across the Gulf coast in advance of a
cold front, but destabilization will likely remain insufficient for
deep convection.

$$
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ACUS01 KWNS 221943
SWODY1
SPC AC 221941

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0141 PM CST Mon Feb 22 2021

Valid 222000Z - 231200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN
NORTH CAROLINA INTO SOUTHEAST VIRGINIA...

...SUMMARY...
Isolated strong wind gusts remain possible with a narrow band of showers/thunderstorms this afternoon across eastern North Carolina
and southeast Virginia.

...Eastern North Carolina through southeast Virginia...

Only minor changes have been made to previous forecast which remains
on track. A forced band of low-topped convection extends from
southeast VA through eastern NC. Some increase in reflectivity along
the leading band has been noted. This convective band is embedded
within deep forcing for ascent and strong wind profiles accompanying
a progressive shortwave trough. Some of this momentum might remain
capable of reaching the surface due to precipitation loading and
modest evaporative cooling within the heavier bands as evidenced by
the 41 kt gust at Wakefield VA. However, overall severe threat will
remain limited due to the very marginal thermodynamic environment.

..Dial.. 02/22/2021

.PREV DISCUSSION... /ISSUED 1021 AM CST Mon Feb 22 2021/

...Eastern NC/southeastern VA this afternoon...
A midlevel trough and associated surface cold front/trough now
crossing the Appalachians will continue eastward to the Mid-Atlantic
and southeast Atlantic coasts late this afternoon into early
tonight. Strong forcing for ascent along the front (represented by
the current band of precipitation across the Piedmont), and modest
low-level warming/destabilization to its east, will support a band
of low-topped convection this afternoon from southeast VA into
eastern NC. There should be enough cloud breaks to allow surface
temperatures to warm into the upper 50s across southeastern VA to
lower 60s across eastern NC, as boundary-layer dewpoints increase to
the 50-55 F range within a modifying air mass off the western
Atlantic. This will result in weak surface-based buoyancy (SBCAPE
of 100-250 J/kg), and convection may become deep enough for charge
separation and isolated lightning flash potential. Regardless of
the presence of lightning, very strong low-midlevel winds could be
transported to the surface in the shallow convective band.

Otherwise, the cold front will move southeastward into south
GA/north FL later this afternoon and continue southward into central
FL by early Tuesday. Air mass modification will continue through
the day and into tonight ahead of the front, but the depth of
buoyancy and lightning potential are somewhat in question across FL
given the warm temperature profiles in the 800-650 mb layer, and the
stronger forcing for ascent passing well to the north of FL.

$$
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ACUS01 KWNS 231954
SWODY1
SPC AC 231953

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0153 PM CST Tue Feb 23 2021

Valid 232000Z - 241200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms remain possible across the Pacific Northwest
and northern Rockies this afternoon and evening.

...Discussion...

Only minor adjustments have been made to previous forecast.

..Dial.. 02/23/2021

.PREV DISCUSSION... /ISSUED 1008 AM CST Tue Feb 23 2021/

...Synopsis...
An initial shortwave trough will move east-southeastward over the
Dakotas today to the upper MS Valley tonight, as an upstream trough
digs south-southeastward from BC to he northern Rockies through
tonight. Morning soundings from WA/MT and southern BC/AB show steep
midlevel lapse rates of 8-9 C/km in association with cold midlevel
temperatures (-32 to -38 C at 500 mb) on the cyclonic side of the
mid-upper jet. Even modest daytime heating/mixing will contribute
to weak surface-based CAPE from the WA Cascades eastward to western
MT, where convective snow/rain showers are expected. Though CAPE
will be limited to 100-200 J/kg, the cold profiles will allow
sufficient cloud depth for isolated lightning flashes with the
deeper convective cells, primarily this afternoon/evening.

Otherwise, a slow-moving front will linger near the southeast FL
coast through tonight. A slightly pre-frontal band of convective
showers will move just southeast of the mainland coast/Keys by
midday, but there will still be potential for isolated thunderstorm
development along the front near the coast this afternoon.

$$
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ACUS01 KWNS 241938
SWODY1
SPC AC 241936

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0136 PM CST Wed Feb 24 2021

Valid 242000Z - 251200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
The risk for thunderstorms is low today across the continental U.S.

...20Z Update...
A few lightning flashes were observed over the past hour across
southeast IN along the leading edge of a fast-moving cold front. A
strike or two along the front will remain possible for the next few
hours, but overall coverage is still expected to remain below 10%.
Prevailing forecast of thunderstorm coverage less than 10% across
the remainder of the CONUS also persists.

..Mosier.. 02/24/2021

.PREV DISCUSSION... /ISSUED 1009 AM CST Wed Feb 24 2021/

...Synopsis...
A midlevel shortwave trough over ID this morning will progress south-southeastward to the Four Corners by Thursday morning. Cold
midlevel temperatures with this trough and steep lapse rates will
support some convective snow showers across the northern Rockies,
but profiles will generally be too cold for lightning production.
Farther south, a dry environment suggests that substantial buoyancy
is unlikely to develop in the zone of ascent preceding the midlevel
trough. Elsewhere, shallow/warm process showers will continue along
a stalled front near the southeast FL coast. However, warm midlevel temperatures will limit the depth of the convection and the
potential for charge separation/lightning flashes. Similarly, very
warm temperatures at the base of an elevated mixed layer will
inhibit deep convection along cold front across TX.

$$
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ACUS01 KWNS 251958
SWODY1
SPC AC 251956

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0156 PM CST Mon Jan 25 2021

Valid 252000Z - 261200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING
ACROSS PARTS OF NORTHEASTERN MISSISSIPPI AND NORTHWESTERN ALABAMA
INTO MIDDLE TENNESSEE...

...SUMMARY...
A few severe thunderstorms are possible this evening within a
corridor across northeastern Mississippi and northwestern Alabama
into middle Tennessee. This includes a risk for potentially
damaging wind gusts and perhaps a couple of tornadoes.

...20Z Outlook Update...
Adjustments to the categorical and probabilistic outlook lines were
made to account for the progression of synoptic and sub-synoptic
features, and latest trends concerning ongoing destabilization.

...Mid South vicinity...
Low-level moisture return is ongoing on southerly return flow across
the lower Mississippi into Tennessee Valleys. This appears to be
contributing to modest boundary-layer destabilization (including
CAPE up to 500-1000 J/kg), which is expected to continue developing northeastward as an initial short wave impulse, which has emerged
from the Southwest, progresses east-northeast of the central Great
Plains late this afternoon and evening. As the associated frontal
wave migrates into the lower Ohio Valley, there appears a window of
opportunity for vigorous convective development focused along/just
ahead of the trailing surface trough across Tennessee into
Mississippi. This may coincide with a 40-50 kt southerly 850 mb jet
axis, along which enlarged low-level hodographs may become support
of supercells structures accompanied by the risk for damaging wind
gusts and/or a couple of tornadoes. With the influence of the
mid/upper forcing on the warm sector expected to be
glancing/short-lived, it appears this risk will be maximized this
evening, but at least some severe weather potential may linger as
remnant convection spreads eastward/southeastward overnight.

...Arizona...
A corridor of modest boundary-layer destabilization is ongoing
across the international border into southern Arizona, ahead of the
vigorous short wave impulse now turning inland of the southern
California coast. Coincident with strengthen of west-southwesterly
flow to 30-40+ kt in the 850-700 mb layer, the environment may
become conducive for isolated thunderstorm development with the
potential to produce strong surface gusts approaching or briefly
exceeding severe limits.

..Kerr.. 01/25/2021

.PREV DISCUSSION... /ISSUED 1025 AM CST Mon Jan 25 2021/

...TN Valley today...
A progressive shortwave trough continues to move across the central
Plains today, with an associated 100kt+ mid level jet extending from
north TX into MO. The primary surface low for this system is over
northwest AR, with a warm front extending eastward along the KY/TN
border. Strong low-level wind fields are present across the warm
sector, with sufficient CAPE to pose a marginal risk of a few
fast-moving storms capable of gusty winds. However, model guidance
continues to suggest that slight veering in the low-level winds will
weaken convergence/forcing and limit coverage of deep convection.

...MS/AL/TN this evening and tonight...
After dark, a few thunderstorms are expected to form over parts of
MS/Al and middle TN along/ahead of the advancing cold front.
Low-level and deep-layer vertical shear profiles in this area will
be favorable for storm organization/rotation, and will maintain the
marginal probabilities for isolated tornadoes or damaging wind
gusts. The primary forecast concern in this region will be storm
coverage, and poor thermodynamics in the lowest 3-4 km suggest that
updrafts may struggle to intensify. This area will continue to be
evaluated in later outlooks.

$$
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ACUS01 KWNS 261956
SWODY1
SPC AC 261955

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0155 PM CST Tue Jan 26 2021

Valid 262000Z - 271200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON INTO TONIGHT ACROSS PARTS OF THE FLORIDA
PANHANDLE...SOUTHERN GEORGIA...SOUTHERN SOUTH CAROLINA...

...SUMMARY...
A couple of strong thunderstorms could still impact a narrow
corridor across the Florida Panhandle and parts of southern Georgia
into southern South Carolina late this afternoon into tonight,
accompanied by some risk for severe weather.

...20Z Outlook Update...

...Southeast...
Thunderstorms through this afternoon have been mostly confined to
the vicinity of a narrow plume of higher precipitable water
returning around the northern periphery of the subtropical ridge.
Pre-frontal destabilization over land, aided by daytime heating, has
been generally weak, but in the presence of strong deep-layer shear.
While low severe weather probabilities are being maintained along
this corridor into early evening, the Rapid Refresh, supported by
area VWP data, suggests that low-level flow is in the process of
weakening. An appreciable increase in severe weather potential
seems unlikely, and strongest thunderstorms may tend to remain
focused near the coastal waters south/west of Panama City through
Pensacola, aided by inflow (albeit perhaps slightly elevated above a
stable near surface layer) of higher moisture content/potential
instability. Otherwise, in advance of the significant short wave
trough accelerating northeast of the southern Rockies tonight,
strengthening lower/mid tropospheric warm advection may support
increasing thunderstorm activity, mostly to the cool side of the
stalling surface frontal zone, across parts of southern Mississippi
through north central Georgia.

...Southeast Arizona into southern Rockies...
While convection capable of producing a flash or two of lightning
might still be possible across southeastern Arizona through 20-22Z,
the relatively compact mid-level cold core appears in the process of
the shifting northeastward into southwestern New Mexico, with
mid-level warming underway in its wake. As the larger-scale
mid-level thermal trough continues overspreading the higher terrain
of New Mexico this afternoon, forecast soundings suggest that
thermodynamic profiles might become conducive for some convection
capable of producing lightning. However, eastward into the high
plains, this potential appears likely to become increasingly
negligible.

...Northern California coast...
Some lightning is evident in convection along the occluding surface
front offshore, which might spread into northern California coastal
areas by early evening. Otherwise, post-frontal cooling aloft may
contribute to isolated thunderstorm activity approaching coastal
areas toward 12Z Wednesday.

..Kerr.. 01/26/2021

.PREV DISCUSSION... /ISSUED 1025 AM CST Tue Jan 26 2021/

...FL/AL/GA/SC...
Deep southwesterly tropospheric flow is present today over much of
the eastern CONUS, with the primary mid level jet extending from TX
into the upper OH Valley. A surface boundary extends from southern
SC southwestward into parts of southern GA, southeast AL, and the FL
panhandle. A moist and marginally unstable air mass remains along
and south of the boundary, with a few breaks in the clouds possible
this afternoon. This will provide sufficient CAPE and forcing for
scattered afternoon thunderstorms across the MRGL risk area. Flow
fields are strong but veered. This would suggest that locally
gusty/damaging winds are the main concern, although an isolated
tornado is possible.

Mid level heights will rise slightly this evening in between
systems, before the next upper trough begins to approach AL/FL
panhandle late tonight. Low level winds will strengthen before dawn
in this area, with the potential for redevelopment of a few
thunderstorms - with some risk of gusty/damaging wind or an isolated
tornado.

$$
--- SBBSecho 3.12-Linux
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ACUS01 KWNS 271933
SWODY1
SPC AC 271932

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0132 PM CST Wed Jan 27 2021

Valid 272000Z - 281200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON ACROSS PARTS OF NORTHEASTERN FLORIDA...

...SUMMARY...
An isolated strong storm may continue to pose a risk for severe wind
gusts and/or an additional tornado or two across parts of
northeastern Florida through about 4-5 PM EST.

...20Z Outlook Update...
Primary lingering severe weather potential appears in association
with the small, organized cluster of thunderstorms (with a sustained significant embedded mesoscale vortex) currently propagating
eastward near the Interstate 10 corridor of northeastern Florida.
This probably will include a continuing risk for damaging wind
gusts, and perhaps an additional brief tornado or two, as it passes
near/west and southwest of the Jacksonville area through 21-22Z.
(For further details see SPC Mesoscale Discussion 40)

This cell may be near the southern periphery of the stronger
mid-level height falls, with warmer temperatures aloft and weaker
large-scale forcing for ascent limiting convective potential farther
to the west and south.

Otherwise, adjustments to the categorical and probabilistic lines
have been mostly to account for the progression of the synoptic and
subsynoptic features.

..Kerr.. 01/27/2021

.PREV DISCUSSION... /ISSUED 0957 AM CST Wed Jan 27 2021/

...FL/GA...
Morning surface analysis shows a boundary extending from the FL
panhandle east-northeastward to the GA coast. Scattered showers and
occasional thunderstorms have been occurring in vicinity of this
boundary, including a few rotating/bowing structures. Local VAD
profiles suggest that low level winds are relatively veered,
limiting the convergence along the boundary and the near-surface
vertical shear profiles. Abundant cloud cover will also likely
persist through the day, limiting substantial destabilization. CAM
solutions suggest that deep convection will track across southern
GA/northern FL through the afternoon. A severe storm or two is
possible in this corridor, with locally damaging wind gusts the main
threat. An isolated tornado is also possible, but the overall
severe threat appears to remain marginal.

$$
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ACUS01 KWNS 281617
SWODY1
SPC AC 281615

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1015 AM CST Thu Jan 28 2021

Valid 281630Z - 291200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
A few thunderstorms are possible across portions of central and
southwestern California.

...CA...
No changes have been made to the ongoing forecast. An upper trough
is currently off the CA coast, and will spread inland through the
afternoon and night. Cold temperatures aloft, steepening lapse
rates, and large scale forcing will result in widespread showers
across much of CA, with a few convective elements occasionally
reaching sufficient depth to produce lightning. No severe storms
are forecast.

..Hart.. 01/28/2021

$$
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ACUS01 KWNS 291957
SWODY1
SPC AC 291955

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0155 PM CST Fri Jan 29 2021

Valid 292000Z - 301200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Weak thunderstorm development remains possible across parts of the
Southwest into Great Basin late this afternoon and evening, with
weak thunderstorms also possible across parts of the south central
Great Plains overnight.

...20Z Outlook Update...
Some adjustments to the categorical (10 percent probability)
thunderstorm line have been made to account for the progression of
the synoptic features, and latest trends concerning ongoing
destabilization.

Large-scale mid-level troughing, including a significant
smaller-scale impulse just now in the process of advancing inland of
the southern California coast, may be accelerating
east-northeastward a bit farther north than generally indicated by
prior model output.

Beneath a lead smaller-scale impulse, weak boundary-layer
destabilization is occurring, northward across portions of
southern/eastern Nevada. This is contributing to deepening
convective development, in an environment where thermodynamic
profiles may become marginally conducive to lightning for a few
hours late this afternoon.

Otherwise, as the more significant trailing impulse progresses
inland, it appears that the onset of mid-level warming may
contribute to diminishing risk for thunderstorms near southern
California coastal areas as early as 22-23Z. The extent of the risk
for thunderstorms eastward across the lower Colorado Valley into
Arizona is becoming more unclear due to at least some offset of the
diurnal heating cycle with the arrival of the stronger mid-level cooling/forcing for ascent. However, at least isolated thunderstorm development still appears possible by this evening.

Farther east, precipitation associated with moistening and
large-scale ascent above an elevated mixed-layer, is stabilizing
mid-level lapse rates across parts of the Texas South
Plains/Panhandle vicinity. However, the onset of mid-level cooling
and strengthening lower/mid tropospheric forcing for ascent may
contribute to weak thunderstorm development toward the 03-06Z time
frame, before spreading northeastward overnight.

..Kerr.. 01/29/2021

.PREV DISCUSSION... /ISSUED 1030 AM CST Fri Jan 29 2021/

...Southern California into Arizona...

Upper trough moving into southern CA this morning will continue into
AZ this evening. Ascent and steep mid-level lapse rates accompanying
the primary vorticity maximum are spreading into southern CA, where
isolated thunderstorms should persist this afternoon. The risk for a
few thunderstorms will spread into AZ as lapse rates steepen by late
afternoon into the evening.

...Southern Plains region...

Steep lapse rates (7.5-8 C/km) in the 700-500 mb layer are in place
across the Southern Plains. Though low-level moisture is limited, a
plume of mid-upper level subtropical moisture is spreading northeast
ahead of the southwestern U.S. upper trough. A few lightning flashes
remain possible today with shallow mid-level convection developing
in this plume. The primary corridor of thunderstorm development is
expected late tonight from the Texas Panhandle and northwest Texas
through western and central OK. Deeper forcing for ascent within a strengthening warm advection regime and approach of the shortwave
trough will promote destabilization in the 700-300 mb layer, and
scattered thunderstorms will likely develop, primarily after 08Z.

$$
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ACUS01 KWNS 301247
SWODY1
SPC AC 301245

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0645 AM CST Sat Jan 30 2021

Valid 301300Z - 311200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
FROM NORTHEAST OK AND SOUTHEAST KS INTO SOUTHWEST MO AND NORTHWEST
AR...

...SUMMARY...
Isolated severe thunderstorms will be possible this afternoon and
early evening from northeast Oklahoma into southwest Missouri,
including parts of southeast Kansas and northwest Arkansas.

...OK/KS/MO/AR this afternoon...
A well-defined midlevel trough over the TX Panhandle this morning
will continue east-northeastward over OK/KS today and MO/AR this
evening, before slowing over the lower OH Valley tonight as the
larger-scale pattern begins to amplify upstream (pronounced height
rises over Intermountain West). An associated surface cyclone will
likewise develop eastward along the KS/OK border today, reaching
southwest MO this evening and southern IL late tonight. Low-level
moisture return within the warm sector of the cyclone has been muted
by ongoing air mass modification over the Gulf of Mexico in the wake
of a prior frontal intrusion. However, midlevel moistening and
lapse rates have been sufficient to support clusters of elevated
thunderstorms (rooted near 700 mb) this morning in the zone of
ascent preceding the midlevel trough.

The swath of elevated thunderstorms will likely persist into the day
across OK/KS and overspread MO/AR this afternoon. In the wake of
the elevated convection, a zone of surface heating along a dryline
will overlap a narrow corridor of boundary-layer dewpoints of 50-55
F from southeast KS across northeast OK, from roughly midday into
the afternoon. Destabilization in this narrow corridor could be
sufficient for surface-based convection to develop near and
immediately south of the surface cyclone. Steep low-midlevel lapse
rates and 500 mb temperatures of -20 C and colder should allow
MLCAPE of 250-500 J/kg, with a brief window of opportunity for
low-topped supercells within the left-exit region of the midlevel
jet. Isolated damaging gusts and large hail, as well as an isolated
tornado, will be possible this afternoon with peak buoyancy, before
diminishing rapidly this evening with eastward extent and the onset
of nocturnal cooling.

..Thompson/Broyles.. 01/30/2021

$$
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ACUS01 KWNS 310034
SWODY1
SPC AC 310033

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0633 PM CST Sat Jan 30 2021

Valid 310100Z - 311200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected the remainder of tonight.

...01z Update...

Strong upper trough has progressed into the Mid MS Valley early this
evening, currently extending from northwest MO-northern AR. As a
result, focused exit region of the mid-level jet has shifted into
the lower OH Valley as evident by the extensive precip shield along
the nose of the LLJ.

Upstream, the loss of diurnal heating will prove detrimental to
surface-based convection immediately ahead of the upper trough as boundary-layer cooling cripples an otherwise weakly buoyant air
mass. Remnants of earlier severe that developed over northeast OK
has progressed into the MO Ozark Plateau where substantial weakening
has been observed. With downstream surface temperatures in the 40s
to lower 50s, there appears to be limited buoyancy for robust
updrafts. For these reasons, severe probabilities are too low to
warrant a continuation of the MRGL Risk tonight.

..Darrow.. 01/31/2021

$$
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ACUS01 KWNS 311249
SWODY1
SPC AC 311248

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0648 AM CST Sun Jan 31 2021

Valid 311300Z - 011200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are unlikely through tonight.

...Southeast through tonight...
A midlevel trough over the OH Valley this morning will amplify
southeastward toward the southern Appalachians, in response to
upstream height rises over the Rockies. The initial surface cyclone
will move eastward across the OH Valley and weaken by later today,
and secondary cyclogenesis is expected by tonight along a Carolinas
coastal front. A trailing cold front will move southeastward across
MS/AL today, and then across south GA and north FL tonight. The
primary focus for deep convection will be along this trailing cold
front, and the path of the secondary cyclone along the Carolinas
coastal front.

Low-level moisture return across the Gulf coast and Southeast has
been rather limited thus far, in the wake of a prior frontal
intrusion. Some shallow convection will be possible today along the
front in AL, though poor lapse rates aloft will limit the depth of
buoyancy and the potential for charge separation/lightning.
Low-level moistening and destabilization should become sufficient
for thunderstorms from the FL Big Bend into south GA later this
afternoon into tonight. Convection should also increase by tonight
near and just off the coast of the Carolinas, as the deepening
cyclone encounters a modifying air mass from the western Atlantic.
An isolated severe storm cannot be completely ruled out this evening
and early tonight across north FL/south GA given fairly strong
southwesterly deep-layer shear, but the severe-storm threat will
ultimately be limited by weak buoyancy.

..Thompson/Broyles.. 01/31/2021

$$
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ACUS01 KWNS 011938
SWODY1
SPC AC 011936

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0136 PM CST Mon Feb 01 2021

Valid 012000Z - 021200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized thunderstorm potential is not expected the remainder of
today or tonight.

...20z Update...

The ongoing forecast remains on track and no changes have been made.
For more details, see the previous discussion below.

..Leitman.. 02/01/2021

.PREV DISCUSSION... /ISSUED 0948 AM CST Mon Feb 01 2021/

...Synopsis...
The general thunder line was removed from the southeast Florida
Peninsula as a surface cold front continues to usher convection away
from the Florida Keys. As a high-amplitude mid-level trough and
associated surface cyclone continue to advance eastward across the
eastern U.S, cold surface temperatures and an eastward moving upper
ridge across the central U.S will mitigate deep-moist convective
development across the CONUS. A lightning flash or two may occur
within the moist conveyer belt wrapping around the aforementioned
surface cyclone along the New England Coastline through the
remainder of the period. Similarly, a lightning flash cannot be
completely ruled out across portions of the Pacific
Northwest/northern California coastline this evening into tomorrow
morning with the approach of an upper trough accompanied by scant
buoyancy.

$$
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ACUS01 KWNS 021947
SWODY1
SPC AC 021945

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0145 PM CST Tue Feb 02 2021

Valid 022000Z - 031200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated, non-severe thunderstorms will remain possible along the
Pacific Northwest coast through tonight.

...Synopsis...
No changes have been made to the ongoing forecast.

..Gleason.. 02/02/2021

.PREV DISCUSSION... /ISSUED 1015 AM CST Tue Feb 02 2021/

...Pacific Northwest coast...
A lead shortwave impulse will progress inland towards the northern
Rockies, while the primary shortwave trough will dig southeast along
the British Columbia coast and reach the OR coast by 12Z Wednesday.
This will maintain a steep low to mid-level lapse rate environment
coincident with scant buoyancy along both the OR/WA coast through
much of the period. Scattered showers are expected to persist this
afternoon and likely become more numerous tonight as large-scale
ascent increases downstream of the latter trough. While CG lightning
has not yet been detected, sporadic flashes will be possible and may
result in isolated thunderstorm coverage. Weak effective shear
coincident with the meager buoyancy is expected to preclude
potential for severe.

$$
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ACUS01 KWNS 031951
SWODY1
SPC AC 031950

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0150 PM CST Wed Feb 03 2021

Valid 032000Z - 041200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms will remain possible this afternoon and
evening across eastern Utah, western Colorado, and vicinity.

...20Z Update...
Only minor changes have been made to the general thunderstorm area
across eastern UT/western CO and vicinity based on latest
observational and short-term model trends.

..Gleason.. 02/03/2021

.PREV DISCUSSION... /ISSUED 1006 AM CST Wed Feb 03 2021/

..Eastern UT/Western CO...
No changes have been made to the ongoing forecast. A strong upper
trough will dig into the northwest states today, with a cold front
pushing southeastward across the Great Basin and into the central
Rockies. Forecast soundings ahead of the front show relatively
steep mid level lapse rates and weak-but-sufficient CAPE for
scattered convection. A few of the showers may become deep enough
for occasional lightning flashes. Very strong tropospheric wind
fields, coupled with daytime heating and steepening low-level lapse
rates suggest that gusty winds may accompany the more intense showers/thunderstorms.

$$
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ACUS01 KWNS 041948
SWODY1
SPC AC 041946

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0146 PM CST Thu Feb 04 2021

Valid 042000Z - 051200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized thunderstorms are not anticipated today.

...20Z Update...
No changes have been made to the ongoing forecast. Although a few
lighting flashes occurred earlier across parts of northern IL, the thermodynamic environment is expected to remain very marginal for
lightning across the Midwest through the rest of the afternoon and
tonight. Farther south across the lower MS Valley, shallow
convection may develop this afternoon along a southeastward-moving
cold front. Forecast soundings suggest that poor low/mid-level lapse
rates will inhibit the vertical depth of these showers, with
thunderstorm potential remaining low.

..Gleason.. 02/04/2021

.PREV DISCUSSION... /ISSUED 1027 AM CST Thu Feb 04 2021/

...MO...
A broad upper trough continues to dig into the central US, with a
cold front moving through northern MO. Scattered thunderstorms
occurred earlier over southern/central MO in a warm-advection region
ahead of the front. However, that area of lift has shifted eastward
and out of the region. Model solutions suggest that scattered
showers will re-develop along/ahead of the front this afternoon over
the same general area. However, forecast soundings indicate very
weak CAPE profiles that lend doubt that storms can become tall
enough for charge separation. While isolated lightning flashes are
possible across parts of IA/IL/MO today, coverage appears too low to
warrant a TSTM outlook area.

$$
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ACUS01 KWNS 061249
SWODY1
SPC AC 061248

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0648 AM CST Sat Feb 06 2021

Valid 061300Z - 071200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING INTO
TONIGHT FOR PARTS OF CENTRAL AND NORTH FL...

...SUMMARY...
Isolated severe thunderstorms capable of producing strong to
damaging winds, a tornado, and some hail may impact parts of the
Florida Peninsula today into tonight.

...Central/north FL this evening through tonight..
A low-amplitude shortwave trough over OK/TX this morning will
progress eastward to the southern Appalachians/Carolinas by early
Sunday morning, with associated surface cyclogenesis expected just
offshore of the Carolinas along a coastal front. Prior to the
cyclone forming off the Carolinas tonight, a warm/moist air mass
will spread northward across the FL peninsula, resulting in
destabilization into central and parts of north FL. Initial
clusters of storms will spread across north FL from the northeast
Gulf of Mexico, in a zone of strengthening warm advection/ascent
along the warm front.

Though low-level lapse rates will be rather modest, sufficient
moistening should occur by tonight for storms rooted very near the
surface along the front. Given MLCAPE near 1000 J/kg, effective
bulk shear near 50 kt, effective SRH near 200 m2/s2 and midlevel
lapse rates in excess of 7.5 C/km, there will be potential for
organized clusters/supercells capable of producing damaging winds,
isolated large hail, and perhaps a tornado. Convection will likely
persist in bands along and ahead of the cold front overnight across
central FL through 12z.

...Southeast FL by early afternoon...
Richer low-level moisture (boundary-layer dewpoints of 68-71 F) will
spread northward across south and central FL today, with the greater destabilization expected across southeast FL the first half of the
day. Isolated thunderstorm development is expected from midday into
this afternoon across interior south FL near the moisture gradient,
as surface temperatures exceed 80 F and boost MLCAPE to near 1000
J/kg, while reducing convective inhibition shown by the 12z Miami
sounding. Meanwhile, effective bulk shear of 35-40 kt and some
low-level hodograph curvature will support a low-end supercell and
severe-storm threat this afternoon.

..Thompson/Broyles.. 02/06/2021

$$
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ACUS01 KWNS 061954
SWODY1
SPC AC 061952

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0152 PM CST Sat Feb 06 2021

Valid 062000Z - 071200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE FLORIDA PENINSULA...

...SUMMARY...
Isolated severe thunderstorms capable of producing strong to
damaging winds, a tornado, and some hail are expected over parts of
the Florida Peninsula today into tonight.

...Discussion...
No appreciable changes appear necessary to the ongoing outlook at
this time, as prior forecast reasoning remains reflective of
currently anticipated severe-weather potential. Convection has
increased over the northeastern Gulf of Mexico, and should gradually spread/expand inland across northern and central Florida. Other
storm development is expected to continue in the vicinity of the northward-moving warm front over central Florida. Low-probability
risk for all three severe hazards, with a few of the strongest
storms, remains evident.

..Goss.. 02/06/2021

.PREV DISCUSSION... /ISSUED 1027 AM CST Sat Feb 06 2021/

...Central/Southeast FL this afternoon...
Only minor changes have been made to the ongoing forecast. A
low-amplitude progressive shortwave trough is noted this morning
over the central Gulf of Mexico moving rapidly eastward toward FL.
Ahead of this system, southerly low level winds are increasing over
FL, aiding in the slow northward progression of a weak surface warm
front. Broken clouds and partial daytime heating is occurring south
of the front, which combined with dewpoints in the lower 70s, will
yield afternoon MLCAPE values of 1000-1500 J/kg. Morning CAM
solutions suggest a few thunderstorms may develop during the
early-mid afternoon over the central peninsula and track toward the east-central coast. These storms would be near the retreating warm
front, and in a vertical shear profiles sufficient for updraft
rotation. These storms could pose a threat of large hail and
gusty/damaging winds.

...Central/Northern FL after dark...
The main cluster of convection associated with the aforementioned
shortwave trough is expected to move into the FL Big Bend region
after dark. Model solutions are in general agreement that these
storms will track east-northeastward along the retreating warm front
through the overnight period. Relatively strong wind fields and
lift in this region suggest a risk of a supercell structures,
capable of damaging wind, hail, and perhaps a tornado or two.

$$
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ACUS01 KWNS 071243
SWODY1
SPC AC 071241

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0641 AM CST Sun Feb 07 2021

Valid 071300Z - 081200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS MORNING
ACROSS CENTRAL FL...

...SUMMARY...
A couple of strong storms are possible across central Florida this
morning.

...Central FL this morning...
In the wake of a midlevel shortwave trough moving quickly over GA
and the Carolinas, a surface cold front will continue to move slowly southeastward across central FL. A primarily pre-frontal band of
storms persists this morning, and this convection will likewise
spread slowly southward through late morning and into early
afternoon. Boundary-layer dewpoints near 70 F are contributing
MLCAPE up to 1500 J/kg as of 12z, in an environment with effective
bulk shear of 45-50 kt. However, vertical shear is expected to
weaken gradually through the morning into the afternoon as low-level
flow veers and weakens over time, in response to the departing
cyclone off the Mid-Atlantic coast. Isolated damaging gusts and
perhaps a tornado cannot be ruled out this morning, but the overall
severe threat is expected to slowly diminish through the day, in
tandem with the weakening vertical shear and weakening forcing for
ascent along and ahead of the cold front.

..Thompson/Broyles.. 02/07/2021

$$
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ACUS01 KWNS 071953
SWODY1
SPC AC 071951

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0151 PM CST Sun Feb 07 2021

Valid 072000Z - 081200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe storms are not expected the remainder of the period.

...Discussion...
As per prior expectations, thunderstorms over southeastern Florida
have diminished over the past couple of hours. With this trend
expected to continue, the MRGL/5% wind risk area is being removed at
this time. Additionally, the thunder area is being trimmed
southward on the northern end, as the weakening cold front continues
to progress slowly southward.

Elsewhere, thunderstorms are not expected.

..Goss.. 02/07/2021

.PREV DISCUSSION... /ISSUED 1011 AM CST Sun Feb 07 2021/

...FL...
A surface cold front continues to sag southward across the
south-central FL peninsula, with a line of thunderstorms noted along
the front. This activity will likely persist through the afternoon,
with a general weakening trend expected as low-level winds
veer/decrease and convergence abates. Gusty winds may accompany the
storms early this afternoon, but the risk of severe storms is low.

$$
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ACUS01 KWNS 081953
SWODY1
SPC AC 081952

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0152 PM CST Mon Feb 08 2021

Valid 082000Z - 091200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe storms are not expected through tonight.

...20Z Update...
The only change to the outlook has been to remove parts of south FL
and the FL Keys from the general thunderstorm area, where convective development appears unlikely through the end of the period.

..Gleason.. 02/08/2021

.PREV DISCUSSION... /ISSUED 1026 AM CST Mon Feb 08 2021/

...Discussion...
Weak elevated warm advection across the Gulf Coast states, in
advance of a weak cyclonic disturbance embedded within broader
longwave cyclonic flow covering the U.S., will result in weak
destabilization across this region. As a result, elevated
convection -- including a few thunderstorms -- may evolve across the
central Gulf Coastal region overnight.

Meanwhile, presence of a weak/remnant surface front over south
Florida, which will gradually drift northward in response to the approaching/weak upper disturbance, will continue to focus showers,
and possibly a couple of thunderstorms over portions of the Florida
Peninsula and adjacent offshore waters.

$$
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ACUS01 KWNS 091927
SWODY1
SPC AC 091926

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0126 PM CST Tue Feb 09 2021

Valid 092000Z - 101200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
A few thunderstorms remain possible this afternoon over northern
Florida and far southern Georgia.

General thunderstorm chances are expected to gradually diminish this
afternoon across northern Florida and southern Georgia as the
larger-scale lift quickly shifts eastward/offshore.

..Jewell.. 02/09/2021

.PREV DISCUSSION... /ISSUED 1029 AM CST Tue Feb 09 2021/

...Northern Florida/southern Georgia...
Scattered thunderstorms will continue across northern Florida and
far southern Georgia through the afternoon near and north of
west/east-oriented boundary, while the potential for warm-sector
thunderstorm development is expected to remain low over inland areas
given limited forcing for ascent/convergence south of the boundary.
As per the 12Z Jacksonville FL observed sounding, sufficient
instability (slightly elevated in nature over inland areas) and
relatively long hodographs may support a few strong storms across
northern Florida and possibly extreme southern Georgia today.
However, relatively weak mid-level lapse rates should limit the
potential for severe-caliber hail, with damaging wind potential also
expected to remain minimal as well given existing cloud cover and a
semi-cool boundary layer inland.

$$
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ACUS01 KWNS 101934
SWODY1
SPC AC 101933

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0133 PM CST Wed Feb 10 2021

Valid 102000Z - 111200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not forecast through tonight across the
contiguous United States.

No changes from the previous outlook thinking.

..Jewell.. 02/10/2021

.PREV DISCUSSION... /ISSUED 1029 AM CST Wed Feb 10 2021/

...Discussion...
The large arctic cyclone over central Canada will continue evolving
over the Prairie Provinces today, with broad/fast/weakly cyclonic
flow extending southward into the central U.S.

Farther south and east, more zonal westerly flow is progged.
Meanwhile, a trough in the southern stream is progged to move across
the Four Corners states and adjacent Baja/northern Mexico through
the period.

At the surface, a weak west-to-east baroclinic zone -- currently
extending across northern Florida and the Gulf Coast region -- will
drift slowly northward, eventually/gradually merging with the arctic
front lingering from the Appalachians southwestward across the lower Mississippi Valley to coastal Texas.

A broad zone of convection -- including occasional/embedded
thunderstorms -- will extend from Texas into the Southeast. Most of
the convection will be elevated atop a stable boundary layer north
of the northward-drifting marine front over the Southeast, and north
of the main arctic front over Texas. A few weak/near surface-based
storms will be possible nearer the Gulf Coast, but modest CAPE/shear
suggests storms will remain disorganized.

Later in the period, an increase in elevated storms may occur over
portions of Texas -- from the Del Rio area southward along the Rio
Grande Valley, and eastward across central Texas. While steeper
lapse rates aloft could support a few stronger elevated updrafts,
and associated risk for hail that could locally approach severe
levels, risk appears too low/isolated to warrant introduction of
MRGL risk/5% hail probability.

$$
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ACUS01 KWNS 121253
SWODY1
SPC AC 121252

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0652 AM CST Fri Feb 12 2021

Valid 121300Z - 131200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms are possible across parts of the Southeast,
for another few hours in deep south Texas, and late overnight near
parts of the northern California and southern Oregon coastline.

...Synopsis/Discussion...
A high-latitude blocking pattern will continue over Canada, in
mid/upper levels, anchored by a high over northern Yukon and a
persistent cyclone centered over southern MB. The "undercutting"
belt of westerlies to its south will persist with zonal to subtly
cyclonic flow across the northeastern Pacific and northern CONUS. A
shortwave trough was evident in that flow belt near 150W, around
40N. This perturbation will penetrate the mean ridge offshore from
the Pacific Coast and move ashore in northern CA and OR between
09-12Z. Associated strong DCVA/cooling aloft is expected, under the
left-exit region of a cyclonically curved upper jet max.
Accordingly steepened low/middle-level lapse rates the last few
hours of the period will lead to around 100-300 J/kg MUCAPE atop the
marine layer, some of which will could deep enough to support
isolated lightning.

Meanwhile, a southern-stream trough now over central/northern MX and
west TX will pivot northeastward and weaken, reaching the western
Gulf by the end of the period. Countless minor vorticity lobes --
some convectively induced/enhanced -- will eject northeastward over
the Gulf and Southeast in the foregoing, gently confluent
southwesterlies. Beneath those, a slow-moving surface frontal zone
was analyzed from a low near MCN southeastward across the GA
coastline, and southwestward over the FL Panhandle to the
northwestern Gulf. The bulk of thunder will remain over the open
Gulf, where air/sea fluxes will optimize low-level theta-e.
However, a broad sheet of low-level warm advection and moisture
transport will persist in extending inland, largely elevated
poleward of the front. Isolated, diurnal, surface-based, but
disorganized thunderstorms also may form in an environment of modest
deep-layer lapse rates and weak buoyancy south of the front in parts
of GA and central/northern FL.

..Edwards.. 02/12/2021

$$
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ACUS01 KWNS 130045
SWODY1
SPC AC 130044

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0644 PM CST Fri Feb 12 2021

Valid 130100Z - 131200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Minimal thunderstorm chances may persist tonight over parts of the
Southeast.

...Synopsis...
Beneath southwest flow aloft, scattered showers and a few
thunderstorms will remain possible near a stalled front from
northern FL into southern GA. Around 500 J/kg MLCAPE exists near the
boundary where dewpoints are in the mid 60s F, and the 00Z sounding
from TLH shows thunderstorm potential with little inhibition.
Increasing warm advection overnight with southwest 850 winds to 40
kt may aid storm chances as activity over the Gulf of Mexico moves
onshore, but most forecast soundings show most unstable parcels will
be elevated given time of day.

..Jewell.. 02/13/2021

$$
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ACUS01 KWNS 131257
SWODY1
SPC AC 131256

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0656 AM CST Sat Feb 13 2021

Valid 131300Z - 141200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF CENTRAL/SOUTHWESTERN FLORIDA...

...SUMMARY...
Strong to marginally severe thunderstorms are possible today through
tonight across parts of central and southwestern Florida.

...Synopsis...
In mid/upper levels, a high-latitude blocking pattern will start to
break down as 1) a high now over northern Yukon redevelops
southeastward across the Northwest Territories and 2) a long-lived
cyclone over southern AB moves slowly eastward to northwestern ON.
As this occurs, a speed max and associated shortwave trough --
initially near the CA/OR coastline -- will dig southeastward in a
strongly difluent upper pattern across the Great Basin today. This perturbation will expand into a synoptic-scale trough by the end of
the period, from the Four Corners region southward across
northwestern MX.

In turn, the mid/upper trough now over southern NM and northwestern
MX -- with embedded 500-mb low apparent over Chihuahua -- should
pivot across northeastern MX and south TX through the period. By
12Z, this trough should reach the middle TX Coast and western Gulf,
while weakening rapidly amidst a broadening cyclonic-flow field
related to the expansive upstream troughing. Downstream, a more-
subtle shortwave trough -- now evident in moisture-channel imagery
over the western Gulf -- will eject east-northeastward over the central/northeastern Gulf, weakening substantially by the time ot
reaches FL around the end of the period.

At the surface, a quasistationary to northward-drifting frontal zone
was drawn across north-central FL just south of a DAB-LEE-CGC line,
and is being overtaken from west-east by a convective complex moving
off the Gulf. A frontal-wave low was drawn behind the convection
near buoy 42039, with slow-moving but strong cold front
southwestward across the north-central/west-central Gulf. This low
should weaken over time, with a new one forming tonight over the
central Gulf along the front, and ahead of the ejecting
southern-stream shortwave trough.

...FL...
A loosely organized band of thunderstorms over coastal areas of
west-central FL -- and adjacent Gulf waters -- will proceed
east-northeastward across the peninsula through the rest of the
morning, offering the threat for isolated strong-severe gusts. A
brief tornado cannot be ruled out near and just south of the frontal
zone, where low-level SRH/vorticity will be relatively maximized
based on the modified TBW wind/thermal RAOB. See SPC mesoscale
discussion 73 for near-term details.

This activity has been very poorly progged by most 00Z convection-
allowing guidance including HREF members, as well as HRRR runs from
then through 10Z, when finally forced by reflectivity input to
depict (underdone) convection initially. The atmosphere clearly is
not obedient to the models. Observationally, based on satellite and
radar trends, associated cloud cover and precip should impede
diurnal destabilization over northern and parts of central FL,
effectively shunting the baroclinic zone southward on the mesoscale
and casting increasing doubt on severe potential with northern
extent.

An additional round or two of strong/isolated severe convection,
with potential for embedded supercells/bow structures, is possible
this afternoon and/or tonight over parts of central/southern FL.
Some of this activity will interact with the boundary reinforced/
relocated southward by morning convection, while also accessing
less-disturbed warm-sector inflow parcels. In the warm sector over west-central/southwestern FL late tonight, forecast soundings
indicate that rich boundary-layer moisture will offset slightly
warming midlevel temperatures (around 500 mb) enough to yield
500-1000 J/kg MLCAPE, though low-level shear/hodographs will
diminish with southward extent. In association with such
convection, a relatively concentrated corridor of potential may
develop within the broader marginal area; however, mesoscale
uncertainties preclude assigning greater unconditional probabilities
at this time.

..Edwards/Smith.. 02/13/2021

$$
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ACUS01 KWNS 131955
SWODY1
SPC AC 131954

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0154 PM CST Sat Feb 13 2021

Valid 132000Z - 141200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM CENTRAL
THROUGH NORTH CENTRAL FLORIDA...

...SUMMARY...
A few strong to severe thunderstorms remain possible this evening
and tonight, mainly across central through north central Florida.

...Central through north central Florida...

The primary change to the previous outlook has been to trim the
threat area slightly on the northern end. As of mid afternoon, a
modifying outflow boundary extends from south of Cape Canaveral
southwestward to near Cape Coral. Objective analysis shows the
strongest instability resides south of this boundary with 1000-1500
J/kg MLCAPE, though some northward recovery is expected into the
evening and overnight. Next round of thunderstorms and accompanying
severe risk is expected overnight as another in a series of impulses
approaches from the west. Extent of northward boundary layer
recovery may be limited by a general weakening of the low-level jet,
loss of daytime heating, and potential for areas of showers to move
inland through northern and north central FL.

..Dial.. 02/13/2021

.PREV DISCUSSION... /ISSUED 1027 AM CST Sat Feb 13 2021/

...FL...
The initial round of strong to local severe potential is progressing
offshore of the Space Coast. In the wake of this round, a
substantial gap in convective activity is anticipated through the
rest of the afternoon. Towards early evening, it is possible that
convection over the northeast Gulf will attempt to develop
east-northeast along the synoptic baroclinic zone across north FL.
Given the stabilizing effects of the lead convection and remnant
cloud coverage currently in its wake, appreciable destabilization
across north FL is questionable. However, cloud breaks are evident
and enough time should exist for weak surface-based buoyancy by late
day. Thus, the extent of the cat 1/MRGL risk area has been
readjusted northward given the presence of the front and adequate
deep-layer shear.

A final round of strong gusts/brief tornado potential may develop
late tonight across a portion of the southwest to west-central coast
before spreading northeast across the central peninsula overnight.
Most guidance suggest strengthening of lower-level (850-700 mb)
moist advection will occur. This will likely be coincident atop the
remnant outflow/leading baroclinic zone from this morning's
convection.

$$
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ACUS01 KWNS 141256
SWODY1
SPC AC 141255

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0655 AM CST Sun Feb 14 2021

Valid 141300Z - 151200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
CENTRAL AND NORTHERN FLORIDA...

...SUMMARY...
Damaging to severe gusts are possible within episodes of
thunderstorms today over central and northern Florida, along with a
slight threat for tornadoes.

...Synopsis...
In mid/upper levels, broadly cyclonic flow will continue across much
of the central CONUS and MX, on either side of a progressive
synoptic trough. The trough was located at 12Z from western CO south-southwestward across eastern AZ and the central/northern Gulf
of California. By 12Z tomorrow, this trough should extend across
central KS, southwestern OK, west-central TX, and north-central to
west-central MX. Downstream, a broad fetch of southwesterly flow
will cover most of the eastern CONUS, Gulf of Mexico and FL.
Several minor vorticity lobes/maxima will eject northeastward within
that belt, across the Gulf and Southeast.

The two most prominent embedded shortwave troughs were apparent in moisture-channel imagery near the FL West Coast and over the west-
central Gulf. This feature will proceed northeastward to the
Atlantic over the next several hours and deamplify. Meanwhile, the
upstream perturbation should eject northeastward across the central/
northern Gulf as a weakening, negatively tilted perturbation,
reaching southern portions of MS/AL and northwestern FL by 00Z, then accelerating northeast and essentially dissipating overnight.

At the surface, somewhat wavy, quasistationary front extended
east-northeast to west-southwest across north-central FL, then to a frontal-wave low over the north-central Gulf south of the
Mississippi River mouth, then well offshore from BRO. Over FL, this
boundary may move slightly northward as a warm front today as the
surface low approaches, then once the low is past Fl by mid/late
afternoon, the front should move little or just slightly southward
again. This evening, ahead of the major trough aloft, a stronger
frontal-wave low will form over the Gulf east of BRO, and ripple
northeastward along the front to shelf waters south of ARA or HUM by
12Z.

...FL...
South of the front, an outflow boundary that had been drawn across
central FL near a PIE-DAB line has been diffused by convection that
since has crossed FL on both sides of the boundary. Large-scale
ascent ahead of the leading perturbation has been contributing to a
favorable environment for showers and mostly non-severe
thunderstorms all night into early this morning over FL, except for
a briefly tornadic supercell near PIE around 06Z, along the southern
boundary.

Near-surface airmass recovery -- driven both by warm advection and
muted diurnal surface heating under cloud cover -- is expected
across central and parts of northern FL behind the morning
convection. Associated destabilization will combine with a
moisture-rich low-level profile south of the synoptic front to
offset modest midlevel lapse rates, enabling deep buoyancy.

Severe potential with the next round(s) of convection, from midday
through afternoon, will decrease with southward extent due to weaker
deep shear and low-level shear, and with northern extent past the
front into unsuitably stable near-surface conditions. The corridor
of most-favorable parameter spaces still appears to be across parts
of central and north-central FL. Weak MLCINH and MLCAPE around
1000-1500 J/kg should develop. Patches of 150-250 J/kg effective
SRH will support a few supercells and small bows embedded in an
otherwise rather messy convective pattern. Activity should diminish
this evening and overnight due to a combination of slow surface
stabilization and lack of robust support aloft, southeast of the
weakening mid/upper perturbation.

..Edwards/Smith.. 02/14/2021

$$
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ACUS01 KWNS 150046
SWODY1
SPC AC 150044

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0644 PM CST Sun Feb 14 2021

Valid 150100Z - 151200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe storms are no longer expected through Monday morning.

...Southeast...
As the lead wave continues to move northeast across the Mid
Atlantic, lift will continue to decrease over FL. The 00Z soundings
show a pronounced subsidence inversion in the midlevels. Therefore,
while still moist and unstable over the peninsula, storms should
remain concentrated over the Atlantic along the cold front.

Elsewhere, elevated thunderstorms are expected to increase in
coverage from southeast TX into the lower MS Valley tonight, as
large-scale lift increases ahead of a powerful upper trough. Given
the cold air already in place at the surface, severe storms are
unlikely.

..Jewell.. 02/15/2021

$$
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ACUS01 KWNS 151632
SWODY1
SPC AC 151630

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1030 AM CST Mon Feb 15 2021

Valid 151630Z - 161200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FL PANHANDLE
INTO SOUTHWEST GA INTO EARLY EVENING...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS COASTAL CAROLINAS OVERNIGHT...

...SUMMARY...
Scattered damaging winds and a few tornadoes are likely across the
Florida Panhandle into south Georgia through early evening. A strong
tornado or two is possible. Severe thunderstorms are also possible
across north Florida and overnight into the coastal Carolinas.

...FL Panhandle to south GA...
Upgraded to cat 3/ENH risk for the potential of a strong tornado or
two along with scattered damaging winds likely, a few of which may
be significant.

Scattered thunderstorms are underway from the surface cyclone that
is near the far southeast tip of LA into the north-central Gulf
along a sharp cold front. Additional convection may also develop
within the next couple hours ahead of this activity within
pre-frontal bands of confluence evident in visible satellite
imagery. As the surface cyclone deepens towards the AL/GA/FL border
area, the warm front should advance inland across the FL Panhandle
reaching southern GA by early evening. Mid to upper 60s F surface
dew points are expected in that regime, supporting a pronounced
gradient of MLCAPE from north to south, approaching 1500 J/kg along
the coast. Expect strengthening mid/upper winds supporting 50-65-kt southwesterly effective-shear vectors, oriented just slightly
rightward of the main corridor of convective forcing with an
elongated mid/upper-level portion of the hodograph. The southern
fringe of a 45-60-kt LLJ will contribute to low-level hodograph
curvature with 200-400 m2/s2 effective SRH, greatest along the warm
front.

Pervasive stratus north of the warm front renders uncertainty over
the degree of tornado coverage as near-surface lapse rates may
remain less than ideal. However, the preceding favorable factors may
compensate and a conditional risk for a strong tornado or two is
apparent this afternoon. The tornado threat should subside some this
evening as the primary surface cyclone occludes across the western
portion of the Appalachians with the shortwave trough progressing
rapidly northeast away from the region.

...Coastal Carolinas...
Elevated thunderstorms should spread northeastward over interior
areas tonight, as a northward extension of the Gulf regime. A
separate, prefrontal low-level convergence zone is forecast to
support increasing thunderstorms tonight and affect coastal areas
through the end of the period. A damaging-gust threat may develop
very near the coastline, where boundary-layer instability may be at
least marginally favorable, with tornado potential from any mature
supercell that can cross the coast. Farther northwestward, isolated strong-severe gusts may penetrate the near-surface stable layer,
with potential diminishing with inland extent.

Along the coast, buoyancy will increase with proximity to the Gulf
Stream, where vertical heat/moisture fluxes will provide the most
sustained air mass modification. Forecast soundings still indicate
shallow near-surface stable layers at the bottom of the lifted layer
yielding surface- based effective-inflow parcels. However, vertical
shear will be favorable, with 45-55-kt effective-shear magnitudes
and effective SRH around 200-300 J/kg.

..Grams/Goss.. 02/15/2021

$$
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ACUS01 KWNS 091956
SWODY1
SPC AC 091954

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0154 PM CST Sat Jan 09 2021

Valid 092000Z - 101200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms will be possible overnight across parts of
central/south Texas.

...Discussion...
No change was made to the previous convective outlook.

..Smith.. 01/09/2021

.PREV DISCUSSION... /ISSUED 1022 AM CST Sat Jan 09 2021/

...Synopsis...
A midlevel shortwave trough near the Four Corners will continue
moving southeastward toward far West TX by Sunday morning.
Low-midlevel moisture and buoyancy are quite limited across the
southern Rockies area with this trough. Farther east, a relatively
cool/dry air mass persists across the Gulf of Mexico in the wake of
a prior frontal passage. Much of the moisture return to TX will be
above the cool air mass at the surface, and forecast soundings
suggest some potential for weak buoyancy rooted near 700 mb
overnight across central/south TX. Thus, a few elevated
thunderstorms will be possible tonight in the zone of ascent/warm
advection in advance of the midlevel trough.

Otherwise, a shortwave trough over the eastern Pacific will approach
the Pacific Northwest coast late tonight and gradually weaken while
moving into the mean ridge position. The primary cold core will
pass to the north of this area, and the only weak buoyancy will be
rooted above the surface in the pre-frontal warm conveyor belt. The
overall thunderstorm threat appears too marginal to justify an
outlook area.

$$
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ACUS01 KWNS 101231
SWODY1
SPC AC 101230

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0630 AM CST Sun Jan 10 2021

Valid 101300Z - 111200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Sporadic non-severe thunderstorms are possible over south Texas and
southern Louisiana.

...Synopsis...
In mid/upper levels, the large-scale pattern will be characterized
by a broad cyclone over the Gulf of Alaska, mean ridging from CA
across the northern Rockies and northwestern Canada, and a complex,
split-flow regime of mean troughing over the central CONUS. The
principal southern-stream perturbation, around which the flow
splits, is evident in moisture-channel imagery over eastern NM and
far west TX, with a nearly closed cyclone around a 500-mb low
located over southeastern NM. The low should close fully through
the remainder of this morning and move eastward across west TX,
reaching the area between CDS-ABI by 00Z. By 12Z, the low should be
near TXK, along a deamplifying shortwave trough, then becoming an
open wave again and weakening across the Mid-South on day 2.

At the surface, a distinct low should develop off Padre Island by
around 18Z, from a trough analyzed at 11Z near a BRO-CRP-SAT axis.
The low should move east-northeastward from there across the
northwestern Gulf, and remaining south of the mainland through the
rest of the period. By 12Z, the low should be located south of
southeastern LA, with warm front arching to just south of the moth
of the Mississippi River, then southeastward over the east-central
Gulf. A cold front will trail south-southwestward from the low
across the northwestern Gulf.

...South TX...
Isolated to widely scattered thunderstorms are possible today across
much of south TX, within a broad plume of elevated, low-level warm
advection and moisture transport wrapping toward the mid/upper low.
This activity will be supported by elevated MUCAPE in the 200-500
J/kg range, rooted around 750-850 mb in southern areas and 650-750
mb from the Edwards Plateau across south-central TX.

A main convective swath -- perhaps a southward extension of the zone
of elevated frontogenetic lift now passing the AQO/SAT/COT corridor
-- should evolve through the day just inland from the lower TX Coast
and shift eastward. This activity should remain elevated and non-
severe over land, behind the developing surface cyclone. The
convection should increase in coverage and intensify after reaching
the Gulf surface low and encountering a higher-theta-e, more
surface-rooted inflow layer of the warm sector. Forecast soundings
suggest that deep shear and CAPE may become favorable for a severe
threat affecting offshore interests well south of the upper TX and
LA Coasts, but should not extend inland/north of the warm front, due
to lack of boundary-layer buoyancy.

..Edwards/Mosier.. 01/10/2021

$$
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ACUS01 KWNS 111929
SWODY1
SPC AC 111928

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0128 PM CST Mon Jan 11 2021

Valid 112000Z - 121200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
The risk for thunderstorms appears negligible across the CONUS.

...Discussion...
No change was made to the previous convective outlook.

..Smith.. 01/11/2021

.PREV DISCUSSION... /ISSUED 0947 AM CST Mon Jan 11 2021/

Relatively dry and stable conditions are expected to preclude
thunderstorm development across the CONUS during the forecast
period.

$$
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ACUS01 KWNS 131954
SWODY1
SPC AC 131953

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0153 PM CST Wed Jan 13 2021

Valid 132000Z - 141200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected through tonight.

...20z Update...

The ongoing forecast remains on track. No changes have been made
with this update. See previous discussion below for forecast
details.

..Leitman.. 01/13/2021

.PREV DISCUSSION... /ISSUED 1019 AM CST Wed Jan 13 2021/

...Southeast States...
A southern-stream upper low is moving across LA/MS today, with its
associated mid level speed max approaching the southeast states.
Lift in the left-exit region of this jet will continue to result in
scattered showers across parts of MS/AL/GA this afternoon and
evening. While an isolated lightning flash is possible, it is
likely to stay below the 10% criteria for a general thunderstorm
outlook.

Later this evening, increasing large-scale ascent will shift
eastward into the Carolinas. Forecast soundings suggest a slightly
deeper unstable layer, along with a deeper moist layer. This may be
sufficient for a better chance of lightning flashes after dark over
parts of SC and southern NC.

$$
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ACUS01 KWNS 251941
SWODY1
SPC AC 251939

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0139 PM CST Thu Feb 25 2021

Valid 252000Z - 261200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS STARTING THIS
EVENING IN NORTH TX AND CONTINUING OVERNIGHT TO THE ARK-LA-MISS...

...SUMMARY...
A few storms capable of producing large hail and isolated strong
wind gusts are expected to form this evening across north Texas, and
then spread eastward to the Ark-La-Miss through tonight.

...20Z Update...
Overall forecast reasoning remains unchanged from the previous
outlook. Increasing low-level warm advection is still expected to
result in elevated thunderstorm development this evening across
north/northeast TX. These storms are forecast to persist throughout
the night, spreading eastward across the Arklatex and into the Mid
MS Valley. A few stronger storms could produce hail. Potential also
exists for a strong downdraft or two in areas near the frontal zone
where the low-level stable layer is not as deep.

..Mosier.. 02/25/2021

.PREV DISCUSSION... /ISSUED 1022 AM CST Thu Feb 25 2021/

...North TX this evening to the Ark-La-Miss overnight...
A midlevel shortwave trough over AZ this morning will accelerate
eastward to the southern High Plains by this evening and the Red
River Valley of TX/OK overnight. In advance of the midlevel trough,
low-level warm advection is expected to increase along and north of
a stalled surface front this evening into tonight, on the nose of a
35-40 kt low-level jet. A warm elevated mixed layer will cap the
warm sector south of the front, but ascent and moistening atop the
frontal surface will support elevated thunderstorm development,
starting this evening across north/northeast TX, and subsequently
spreading eastward across southern AR/northern LA tonight.

The observed midlevel lapse rates in excess of 8 C/km over the
southern Plains, in combination with increasing low-level moisture
from the western Gulf of Mexico, will result in MUCAPE of at least
1000 J/kg to the cool side of the surface front by this evening.
The moderate buoyancy and effective bulk shear in excess of 50-60 kt
will support the potential for elevated supercells capable of
producing at least isolated large hail. The depth of the
cool/stable layer near the ground and somewhat limited DCAPE cast
doubt on the damaging-wind threat, though a few stronger gusts
reaching the ground cannot be ruled out overnight.

$$
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ACUS01 KWNS 261941
SWODY1
SPC AC 261939

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0139 PM CST Fri Feb 26 2021

Valid 262000Z - 271200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are possible this evening and tonight across portions
of the Tennessee Valley.

...20Z Update...

...TN Valley...
Recent satellite imagery shows a well-defined shortwave progressing
through the MS Valley and another emerging out of the central High
Plains. Precipitation shield associated with the lead shortwave
continues to spread eastward into the middle/upper OH Valley and
central Appalachians. Lightning in not expected within this area of
showers. As mentioned in the previous discussion, an additional
round of showers and thunderstorms is anticipated later this evening
as low-level flow and isentropic ascent increase ahead of the second
shortwave. Modest buoyancy should temper overall storm intensity,
but an storm or two could become strong enough to produce isolated
marginal hail.

..Mosier.. 02/26/2021

.PREV DISCUSSION... /ISSUED 1021 AM CST Fri Feb 26 2021/

...TN Valley Vicinity...
A shortwave trough is evident this morning over AR/LA tracking
eastward into the Mid-South. Thunderstorms have been accompanying
this system overnight and this morning, but lightning activity has
diminished greatly during the past few hours. This trend is likely
to continue through the mid/late afternoon as the upper system
de-amplifies. By early evening, southwesterly low-level winds will
strengthen across parts of MS/AL/TN, resulting in renewed potential
for a few thunderstorms tonight. Weak instability should preclude
the risk of severe storms.

$$
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ACUS01 KWNS 271300
SWODY1
SPC AC 271258

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0658 AM CST Sat Feb 27 2021

Valid 271300Z - 281200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN
OKLAHOMA TO THE LOWER OHIO VALLEY...

...SUMMARY...
Isolated severe thunderstorms are possible from eastern Oklahoma to
the lower Ohio Valley this evening into tonight.

...Synopsis...
Mid/upper troughing will amplify and assume more net positive tilt
through the period. A strong shortwave trough -- initially over the
interior Northwest and northern Great Basin -- will dig south-
southeastward and strengthen, resulting in a sharply defined trough
with nearly closed 500-mb low over UT/AZ by 12Z tomorrow. As that
occurs, a leading perturbation -- apparent in moisture-channel
imagery over western WY and eastern UT -- will phase with a lower-
amplitude shortwave to its south and pivot across the central
Plains. To the southeast, a long and broad fetch of southwesterly
flow aloft will be maintained from the southern Rockies and northern
MX across the Mississippi Valley, becoming west-southwesterly to
westerly flow over the Atlantic Coast States.

At the surface, a wavy warm-frontal zone was drawn at 11Z over
eastern/northern AL, northern/western MS, northern LA, and east TX
near LFK, becoming quasistationary southwestward across the lower/
middle TX Coastal Plain. This boundary should shift northward
diffusely and erratically through the period, through the Mid-South
and Arklatex, as well as the TN Valley region. A low should develop
over the central Plains this evening, associated with the ejecting
mid/upper perturbation, and cross IA overnight, with cold front
trailing over eastern MO, eastern/southern OK, and the TX South
Plains by 12Z.

...Eastern OK to Ohio Valley...
A persistent, elongated plume of elevated, low-level warm advection
and moisture transport is apparent in precip fields from AR-WV, and
extends back into east TX. With the ejection of the WY/UT upper
perturbation displaced well northwest of the area, direct upper
support will be minimal. Still, as low-level theta-e advection
persists and the Gulf warm-frontal zone moves poleward, the western
part of regime likewise should persist and shift northward across
northeast TX and AR throughout the day, offering mostly weak
convection and showers.

Thunderstorm potential will increase from late afternoon into
evening as the regime continues to shift northward over the
Arklatex, eastern OK, the Ozarks and Mid-South. This will be
encouraged by strengthening theta-e accompanying a broad, increasing southwesterly LLJ building to the 45-55-kt range (locally stronger).
Frontal lift and isentropic ascent of increasingly moist/unstable
parcels to LFC will foster a growing, intensifying plume of
convection within which the most intense cells will be capable of
severe hail or damaging to marginally severe gusts. Despite the
modest lapse rates aloft over much of the area, isolated marginally
severe hail will be possible given a wind profile suitable for
elevated supercells, with 45-55-kt effective-shear magnitude beneath
the southwest-flow field aloft, and LLJ-enlarged hodographs with
250-400 J/kg effective SRH. A near-surface stable layer will
minimize but not entirely eliminate damaging-gust potential as well.

...Lower Missouri Valley vicinity...
Isolated thunderstorms may develop near the surface low and cold
front tonight across parts of the corridor from northeastern KS
across southeastern NE/northwestern MO into IA. Though large-scale
and frontal forcing will be strong in this area relative to the
other main convective regime described above, the low-level air mass
will be much more moisture-starved. At this time, the barely
adequate buoyancy for elevated thunder (e.g., MUCAPE under 200 J/kg)
appears too limited for unconditional severe potential, especially
with a relatively stable near-surface layer remaining. However, a better-organized, more strongly forced arc of convection than most
progs indicate could penetrate that layer with strong gusts.

..Edwards/Jewell.. 02/27/2021

$$
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ACUS01 KWNS 271950
SWODY1
SPC AC 271948

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0148 PM CST Sat Feb 27 2021

Valid 272000Z - 281200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
EASTERN OKLAHOMA TO WESTERN KENTUCKY...

...SUMMARY...
Isolated strong to severe thunderstorms remain possible from eastern
Oklahoma to western Kentucky this evening and overnight.

...20Z Update...
No appreciable changes have been made to the ongoing forecast.
Elevated storms are expected to continue increasing in coverage this afternoon/evening across parts of eastern OK into AR as low-level
warm advection strengthens in tandem with a south-southwesterly
low-level jet. This activity should eventually spread into southern
MO and the Mid-South tonight while posing an isolated threat for
marginally severe hail and perhaps a strong wind gust or two.
Generally weak instability should tend to limit the overall severe
threat, with convection remaining generally elevated.

..Gleason.. 02/27/2021

.PREV DISCUSSION... /ISSUED 1014 AM CST Sat Feb 27 2021/

...Synopsis...
A large-scale trough across the northern Rockies into the Great
Basin will continue to amplify and dig into the Four Corners today.
As this occurs, a lee trough/cyclone is expected to develop within
the southern/central High Plains. The rather diffuse cyclone will
progress to the northeast into the upper-Mississippi Valley region
by tomorrow morning. While height falls ahead of the trough will not
be overly strong, southerly low-level winds will increase along with
the trough/cyclone and ahead of a southeastward moving cold front
with accompanying warm front advancing northward in the Mid-South.

...Eastern Oklahoma into Western Kentucky...
Moisture return should continue to increase this afternoon and
evening across parts of eastern Oklahoma. Scattered storms are
expected to develop near the intersecting cold and warm fronts in
the vicinity of Fort Smith, AR and points southeastward. This
morning's observed regional soundings show mid-level lapse rates of
7-8 C/km. With strong deep-layer flow and MUCAPE near 1000 J/kg,
large hail will be possible with these elevated storms. A low-end
risk for damaging wind gusts will also exist given the relatively
shallow stable near-surface layer.

Farther east and north, deep-layer flow will be similarly strong,
but these areas will be farther removed from the steeper mid-level
lapse rates, reducing buoyancy. A risk for marginally severe hail
and damaging wind gusts will still exist. Towards tomorrow morning,
forecast soundings do indicate that low-level theta-e advection will
allow ongoing storms to become near surface-based meaning the threat
for damaging wind gusts may be maximized late in the period.

$$
--- SBBSecho 3.12-Linux
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ACUS01 KWNS 281245
SWODY1
SPC AC 281243

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0643 AM CST Sun Feb 28 2021

Valid 281300Z - 011200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
TEXAS TO MIDDLE TENNESSEE AND SOUTHERN KENTUCKY...

...SUMMARY...
Damaging thunderstorm gusts, a few tornadoes and isolated large hail
are possible from northeast Texas to Middle Tennessee and southern
Kentucky.

...Synopsis...
In mid/upper levels, a positively tilted trough is apparent in
moisture-channel imagery from central Canada across the northern/
central Plains and central Rockies to AZ and Baja. A shortwave
trough initially over SD/NE will eject/stretch northeastward across
the Upper Great Lakes through the period, losing amplitude, but
remaining connected to a very lengthy vorticity banner extending
southwestward around the northern/western sectors of a developing
closed cyclone over parts of NM/AZ. The associated 500-mb low
should reach southern NM by the end of the period at 01/12Z.
Farther equatorward, a weak but potentially influential southern-
stream perturbation over Chihuahua should eject northeastward across west-central/north-central TX today.

At the surface, 11Z analysis depicted a surface low near the IA/MN
border with cold front southwestward over southeastern KS,
southwestern OK, and the TX South Plains. By 00Z, the low should
reach ON, just north of Lake Huron, as the center of a well-
developed and deepening synoptic cyclone, with cold front trailing
across Lower MI, IN, the lowest segment of the Ohio Valley, the
Arklatex region, and portions of south-central/southwest TX. By
12Z, the cold front should reach eastern NY, central VA,
northwestern GA, central MS, central LA, the mid/upper TX Coastal
Plain, and deep south TX.

...North TX to TN/KY...
Scattered thunderstorms may develop along/ahead of the cold front as
early as mid/late morning over parts of north TX and southeastern
OK, increasing in coverage and extending northeastward through the
day as the regime both backbuilds southward, shifts eastward and
expands northeastward. An organized belt of scattered to numerous thunderstorms is expected to evolve as a result, by mid/late
afternoon, from the Ozarks across southeastern OK to central/
northeast TX. The foregoing warm sector will destabilize and build
buoyancy through the day from a combination of warm advection,
moisture advection/transport, and modest/erratic surface heating
under broken cloud cover. Surface dew points in the 60s to near 70
F should be common near and south of a decaying warm front now
located over parts of TN, AR and eastern OK, and forecast to become
more diffuse with time. This will contribute to a pre-cold-frontal
plume of MLCAPE 1500-2000 J/kg over the TX part of the outlook,
where midlevel lapse rates will be steepest, and 800-1500 J/kg
elsewhere.

Low-level and deep shear will be favorable, with effective SRH
commonly in the 150-250 J/kg range despite somewhat veered flow just
above the surface, and 60-80 kt effective-shear vectors. The latter
will be aligned with a substantial component parallel to the main
belt of convective forcing, such that a combination of embedded
supercells and QLCS mesocirculations are possible. Those will yield
potential for tornadoes and damaging to severe gusts. Hail will be
more of a concern relatively early in the convective cycle and in
western parts of the outlook area, while modes still are less messy,
and amidst greater lapse rates. The severe potential may continue
through much of the evening before weakening late tonight, except
for the next regime described below.

...South TX tonight...
Isolated to scattered thunderstorms are possible overnight -- mostly
from about 06Z onward -- across portions of the Edwards Plateau, and
adjoining parts of the Rio Grande Valley, northeastward over the
Hill Country. This activity may develop on either side of the cold
front, as strong moist advection via easterly flow occurs mainly in
the 850-950-mb layer. Forecast soundings indicate this process,
underlying steep low/middle-level lapse rates, will yield weak
MUCINH, with MUCAPE ranging from around 1500-2000 J/kg over southern
parts of the outlook area to 500 J/kg in the north. The substantial
easterly component in the inflow layer will contribute to strong
deep shear, with effective-shear magnitudes 60-80 kt possible.
Activity developing on or just south of the front will be undercut
quickly, but may persist long enough to produce large hail. At this
time, coverage of the severe convection is uncertain, so the
unconditional outlook will be maintained at marginal probabilities.

..Edwards/Jewell.. 02/28/2021

$$
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ACUS01 KWNS 281959
SWODY1
SPC AC 281958

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0158 PM CST Sun Feb 28 2021

Valid 282000Z - 011200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
NORTHEAST TEXAS INTO THE MID-SOUTH AND TENNESSEE VALLEY...

...SUMMARY...
Damaging thunderstorm wind gusts, a few tornadoes, and large hail
will remain possible through tonight from northeast Texas into the
Mid-South and Tennessee Valley.

...20Z Update...
Severe probabilities have been reduced behind a southeastward-moving
cold front across parts of north-central/northeast TX and
southeastern OK. Convection is still expected to increase in both
coverage and intensity across AR into western/middle TN and northern
MS this afternoon and evening, with all severe hazards possible. For
more meteorological information on the short-term severe threat
across this region, see Mesoscale Discussion 136. Farther east into central/northern AL and eastern TN, probabilities for damaging winds
and a couple tornadoes have been modestly expanded to account for a
line of storms along the cold front overnight that may still pose an
isolated severe risk.

..Gleason.. 02/28/2021

.PREV DISCUSSION... /ISSUED 1015 AM CST Sun Feb 28 2021/

...Synopsis...
A positively-tilted upper-level trough within the Four Corners
region will continue to sag southeastward today with a closed low
aloft eventually developing across AZ/NM. A broad swatch of strong
mid-level flow will exist from the Texas Big Bend into the Ohio
Valley and lower Great Lakes. At the surface, a cold front extends
from a central WI surface low southeastward into MO/OK and west TX.
The front will be the main focus for severe weather this afternoon.

...ARKLATEX into the Mid-South...
Upper 60s to around 70 F dewpoints are situated to the south of the southeastward moving cold front. Broken cloud cover, particularly in
the ARKLATEX region has allowed temperatures to rise to the low 70s
F. Areas that continue to see broken cloud cover will support
1500-2000 J/kg of MLCAPE this afternoon. Effective shear values of
50-70 kts will support organized storm structures. Deep-layer shear
is generally parallel to the front and will generally favor linear
storm mode, though supercells ahead of and embedded within the line
are possible. Large hail will be possible, particularly early in the
convective cycle. An area of greater hail risk is evident within the
ARKLATEX given this morning's observed upstream mid-level lapse
rates. Very large hail will be possible in this region. Damaging
wind gusts will generally be the primary threat as convection
evolves and grows upscale along the boundary.

Low-level hodographs are supportive of a risk for tornadoes. Again,
the linear storm mode and the weakness in the flow around 700 mb in
both observed and forecast soundings should limit the overall
potential. However, a few embedded supercell and mesovortex
tornadoes within the convective line may occur.

...South TX...
A conditional threat for large hail will exist from the Edwards
Plateau into parts of South Texas. There is continuing uncertainty
with whether storms will develop based on the latest guidance.
However, deep-layer shear will be strong and forecast soundings
indicate very long hodographs. Should storms develop, they will
likely be elevated supercells behind the front.

$$
--- SBBSecho 3.12-Linux
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ACUS01 KWNS 011955
SWODY1
SPC AC 011954

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0154 PM CST Mon Mar 01 2021

Valid 012000Z - 021200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms will remain possible today from parts of Texas across
the Southeast.

...20Z Update...
The only change with this update was to remove portions of central
and south TX from the general thunderstorm area, as additional
convection behind ongoing activity is not expected.

..Gleason.. 03/01/2021

.PREV DISCUSSION... /ISSUED 1006 AM CST Mon Mar 01 2021/

...TX and Gulf Coast Region...
Only minor changes made to the ongoing general thunderstorm forecast
area. Scattered lightning flashes continue to be seen across
central and east TX this morning, beneath the subtropical jet and
ahead of an upper trough approaching from the northwest. This
activity will slowly end from west-to-east, spreading into parts of
LA/MS/AL this evening. Isolated lightning flashes are also possible
this afternoon across parts of northern FL as convection moves in
from the northeast Gulf and forms along/ahead of a weak cold front.
No severe thunderstorms are anticipated today.

$$
--- SBBSecho 3.12-Linux
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ACUS01 KWNS 021954
SWODY1
SPC AC 021952

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0152 PM CST Tue Mar 02 2021

Valid 022000Z - 031200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are possible through tonight across parts of the central/northeastern Gulf Coastal Plain eastward to coastal Georgia,
southern South Carolina and northern Florida.

...Discussion...
Minimal changes were made to the ongoing thunderstorm forecast for
parts of the Southeast.

..Smith.. 03/02/2021

.PREV DISCUSSION... /ISSUED 1026 AM CST Tue Mar 02 2021/

...Southeast...
A compact upper low continues to track eastward across OK/AR, with
large-scale lift affecting much of the southeast states today. This
is resulting in a region of showers and isolated thunderstorms from
southeast LA into MS/AL/GA/FL. This activity will persist through
the afternoon/tonight while moving slowly eastward.

Models are in agreement that a deepening surface low will track
across the northern Gulf of Mexico today, with the associated warm
front just off or barely on shore over the FL panhandle this
evening. This may result in a few strong storms in the coastal
waters or perhaps slightly inland. However, most CAM solutions
suggest the risk of a surface-based storm moving ashore is rather
low, so will maintain the ongoing forecast of less-than 5% coverage
of severe. If a surface-based storm could affect the Big Bend area
of FL, it would pose a risk of damaging winds or a brief tornado.

$$
--- SBBSecho 3.12-Linux
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ACUS01 KWNS 021954
SWODY1
SPC AC 021952

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0152 PM CST Tue Mar 02 2021

Valid 022000Z - 031200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are possible through tonight across parts of the central/northeastern Gulf Coastal Plain eastward to coastal Georgia,
southern South Carolina and northern Florida.

...Discussion...
Minimal changes were made to the ongoing thunderstorm forecast for
parts of the Southeast.

..Smith.. 03/02/2021

.PREV DISCUSSION... /ISSUED 1026 AM CST Tue Mar 02 2021/

...Southeast...
A compact upper low continues to track eastward across OK/AR, with
large-scale lift affecting much of the southeast states today. This
is resulting in a region of showers and isolated thunderstorms from
southeast LA into MS/AL/GA/FL. This activity will persist through
the afternoon/tonight while moving slowly eastward.

Models are in agreement that a deepening surface low will track
across the northern Gulf of Mexico today, with the associated warm
front just off or barely on shore over the FL panhandle this
evening. This may result in a few strong storms in the coastal
waters or perhaps slightly inland. However, most CAM solutions
suggest the risk of a surface-based storm moving ashore is rather
low, so will maintain the ongoing forecast of less-than 5% coverage
of severe. If a surface-based storm could affect the Big Bend area
of FL, it would pose a risk of damaging winds or a brief tornado.

$$
--- SBBSecho 3.12-Linux
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ACUS01 KWNS 031937
SWODY1
SPC AC 031935

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0135 PM CST Wed Mar 03 2021

Valid 032000Z - 041200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms are possible this afternoon over parts of
Florida and near-coastal southern California, and tonight over
northern Arizona.

...Discussion...
No appreciable change was made to the previous convective outlook.

..Smith.. 03/03/2021

.PREV DISCUSSION... /ISSUED 1025 AM CST Wed Mar 03 2021/

...FL...
A weak cold front continues to sag southward across the FL
peninsula, accompanied by a line of showers. Sufficient CAPE is
present to support occasional lightning flashes with this activity,
but none have been recently noted and the overall threat is
diminishing rapidly.

...Southern CA...
A progressive upper low is approaching the coast of southern CA,
with a cluster of showers and isolated thunderstorms noted off the
coast of San Diego and Orange counties. As this activity moves
inland this afternoon, a few lightning flashes are possible.

...Northern AZ tonight...
As the aforementioned upper low moves inland tonight, strengthening
low-level warm advection and lift will promote the develop of a few thunderstorms across northern AZ. No severe storms are expected.

$$
--- SBBSecho 3.12-Linux
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ACUS01 KWNS 041945
SWODY1
SPC AC 041943

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0143 PM CST Thu Mar 04 2021

Valid 042000Z - 051200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS WESTERN OKLAHOMA
INTO PORTIONS OF SOUTHWESTERN KANSAS...

...SUMMARY...
Isolated severe thunderstorms are possible late this afternoon and
evening over parts of the northeastern Texas Panhandle, western
Oklahoma, eastern Oklahoma Panhandle, and southwestern Kansas.

...Discussion...
No appreciable change was made to the previous convective outlook.

..Smith.. 03/04/2021

.PREV DISCUSSION... /ISSUED 1018 AM CST Thu Mar 04 2021/

...Synopsis...
A mid/upper-level trough near the Four Corners will move out onto
the southern Plains and deepen slightly by late afternoon. A surface
cyclone will intensify across the Raton Mesa and move southeastward
roughly along the Red River. Modest moisture return is expected to
the east of a dryline that will advance into western Oklahoma this
evening.

...South-central Plains...
Morning observations continue to show relatively dry surface
conditions across the southern Plains with 50s F dewpoints remaining
along the Texas Gulf Coast. With low-level southerly winds expected
to increase as the surface low deepens, low-level moisture will also
improve during the day and especially as the low-level jet increases
into western Oklahoma late this afternoon. Even so, storms that are
able to form along the dryline/surface trough are likely to be
elevated as lift in the 850-700 mb layer cools and moistens the
profile. With the upper-level low moving overhead, cold temperatures
(around -20 to -23 C) aloft will steepen mid-level lapse rates.
Updrafts will likely be shallow with a few becoming briefly intense
with around 500-800 J/kg MUCAPE. Effective shear across these
updrafts will be sufficient for organized storms capable of
producing large hail. With low levels remaining relatively dry, a
few strong/damaging wind gusts will be possible especially with
earlier activity. Other elevated storm development is possible along
a weak warm front into central Oklahoma. Much weaker buoyancy is
expected to minimize storm intensity, though small hail could occur.

$$
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ACUS01 KWNS 051948
SWODY1
SPC AC 051946

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0146 PM CST Fri Mar 05 2021

Valid 052000Z - 061200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EAST
CENTRAL INTO SOUTHEAST TEXAS AND FAR SOUTHWEST LOUISIANA...

...SUMMARY...
A few thunderstorms capable of producing hail and gusty winds may
develop this afternoon over portions of east-central through
southeast Texas and far southwest Louisiana.

...Discussion...
No appreciable change was made to the previous convective outlook.

..Smith.. 03/05/2021

.PREV DISCUSSION... /ISSUED 1030 AM CST Fri Mar 05 2021/

...East central through southeast Texas...

As of late morning a cold front stretches from a surface low near
Gainesville, south southwestward through east central and south TX.
A warm front extends from the northwestern Gulf into southeast and
south central TX. Partially modified Gulf air with upper 50s to near
60 F dewpoints reside in the warm sector. Visible imagery still
indicates widespread low and mid-level clouds in pre-frontal zone,
but some of these clouds should mix out from the south and west
resulting in a narrow corridor of modest surface heating which
should boost MLCAPE to near 500 J/kg from east central into
southeast TX and possibly far southwest LA. Deeper forcing attending
a vorticity maximum embedded within a cutoff upper low circulation
will move from northwest TX into east central and southeast TX this
afternoon. This should foster thunderstorm development along and
east of the cold front later today. Though winds increase
substantially above 5 km, the anticipated relatively shallow
convective layer should limit effective bulk shear to between 30 and
40 kt. A few cells might develop weak mid-level updraft rotation and
when combined with 7 C/km mid-level lapse rates and modest
instability, could pose some risk for hail. Some clustering of
storms is possible and a few locally strong wind gusts might occur
before activity moves offshore this evening. Overall threat should
remain limited by the marginal thermodynamic environment.

$$
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ACUS01 KWNS 061245
SWODY1
SPC AC 061244

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0644 AM CST Sat Mar 06 2021

Valid 061300Z - 071200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are possible over parts of Florida and the northern
Rockies.

...Synopsis/Discussion...
In mid/upper levels, strong cyclones south of the Gulf of Alaska and
over the eastern QC/Labrador area will anchor mean troughs over the northeastern Pacific and eastern North America, respectively.
High-amplitude ridging in between will shift eastward from the
southern/central Rockies and northern High Plains toward the
southern Plains and upper Mississippi Valley. West of the ridging,
a pronounced shortwave trough -- now evident in moisture-channel
imagery over northern CA and coastal OR -- will continue to eject
away from the oceanic mean trough. This shortwave perturbation
should reach the northern Rockies around 00Z, ahead of which
steepening midlevel lapse rates and meager but sufficient moisture
may support a few instances of lightning.

In the East, a substantial synoptic trough extended from the
Labrador low southwestward down the Appalachians to the north- central/west-central Gulf. This includes a formerly well-developed
closed cyclone when it was over the southern Rockies/Plains, but now
a remnant open-wave perturbation over AL, the western FL Panhandle
and adjoining Gulf. This feature should continue gradual weakening
and move eastward off the FL/GA coastline by 00Z.

At the surface, 11Z analysis showed a wavy, quasistationary frontal
zone across southern FL, west-northwestward to a weak low over the east-central/northeastern Gulf, becoming a cold front from the low
across the west-central Gulf. The low should move slowly east-
southeastward toward the Keys through evening while weakening.
Another low should develops along the front by evening, between
south FL and the northern Bahamas, across which it will move
eastward. Behind the low, the front should move offshore from the
southern peninsula and Keys tonight.

...Southern FL...
Isolated to widely scattered thunderstorms are possible over much of
the central/southern peninsula today into this evening, mostly (but
not entirely) along and south of the front. A few strong
thunderstorms may form near coast from the PBI area southward this
afternoon, then move quickly offshore. Sufficient theta-e should
remain or advect in place to support pockets of 300-800 J/kg MLCAPE
amidst around 35-45-kt effective-shear magnitudes. Buoyancy overall
will be limited by weak lapse rates aloft, with embedded stable
layers such as that observed between 700-800 mb on the 12Z Key West
RAOB.

Weak low-level flow (limiting hodograph size), generally messy
convective mode and lack of greater instability will keep organized
severe potential too conditional and low for a categorical outlook
at this time. The most-unstable boundary-layer air and greatest
unconditional potential for strong/severe thunderstorms will remain
well to the west and southwest of southern FL and the Keys. This
will be near the stem of the Loop Current across the east-central/
southeastern Gulf, where sea-air fluxes will enable the most-buoyant surface-based parcels.

..Edwards/Mosier.. 03/06/2021

$$
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ACUS01 KWNS 062000
SWODY1
SPC AC 061959

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0159 PM CST Sat Mar 06 2021

Valid 062000Z - 071200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR THE EAST
COAST OF SOUTH FLORIDA...

...SUMMARY...
A few strong to locally severe thunderstorms are possible through
the late afternoon near the east coast of south Florida.

...Discussion...
Other than the removal of low-severe probabilities near the Space
Coast in FL, the forecast remains largely unchanged and on track.
See the previous convective outlook for details.

..Smith.. 03/06/2021

.PREV DISCUSSION... /ISSUED 1030 AM CST Sat Mar 06 2021/

...Central/southern Florida Peninsula...
Thunderstorms have developed and increased across the north-central
Florida Peninsula. In spite of weak mid-level lapse rates,
relatively long hodographs accentuated by strong mid-level
westerlies atop east-northeasterly boundary layer winds, coincident
with modest but sufficient buoyancy, could support a few additional
strong to locally severe storms this afternoon across the
east-central Florida Peninsula.

Farther south in a somewhat more moisture-rich air mass, additional thunderstorm development is expected later this afternoon,
particularly across the near-coastal southeast Peninsula. This will
be coincident with relatively long hodographs (35-45 kt effective
shear) and upwards of 500-800 J/kg MLCAPE, which will be potentially
supportive of a few strong to locally severe storms.

$$
--- SBBSecho 3.12-Linux
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ACUS01 KWNS 071229
SWODY1
SPC AC 071228

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0628 AM CST Sun Mar 07 2021

Valid 071300Z - 081200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
A few thunderstorms may occur near the Pacific Northwest Coast.

...Synopsis/Discussion...
In mid/upper levels, the pattern is expected to deamplify over the
eastern CONUS as a strong synoptic trough moves farther out over the
Atlantic, while an upstream ridge crosses Hudson Bay and the Great
Lakes. Still farther upstream, height rises will occur over the
Rockies and High Plains, as a strong Pacific cyclone -- now centered
near 50N138W, digs slowly south-southeastward. A major trough will
continue to extend southward from that cyclone across the northeast
Pacific into subtropical latitudes well west of Baja. Cyclonic
southwest flow aloft, with embedded shortwave perturbations, will
persist over the West Coast.

A related low-level frontal zone and accompanying precip band will
continue to move further inland over WA/OR through the remainder of
this morning, followed by a broad zone of large-scale ascent and
related cooling in midlevels (roughly 700-500-mb), steepening the low/middle-level lapse rates. This will lead to 500-mb temperatures
of -30 to -35 deg C above the cool but moist marine air, supporting
weakly inhibited MLCAPE up to around 200 J/kg, with MUCAPE values
slightly higher. Buoyancy will deepen with time into icing layers
suitable for lightning production, leading to an isolated thunder
potential along the coast and a short distance inland for much of
today into this evening, with the deepest/most-persistent cells.
Thunder potential then should wane as boundary-layer cooling and a
subtle decrease in midlevel lapse rates removes most CAPE.

..Edwards.. 03/07/2021

$$
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ACUS01 KWNS 071935
SWODY1
SPC AC 071934

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0134 PM CST Sun Mar 07 2021

Valid 072000Z - 081200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected, but a few thunderstorms may
occur near the coastal Pacific Northwest.

...Discussion...
No appreciable change was made to the previous convective outlook.

..Smith.. 03/07/2021

.PREV DISCUSSION... /ISSUED 1028 AM CST Sun Mar 07 2021/

...Synopsis/Discussion...
A progressive and only modestly amplified large-scale pattern will
prevail over the CONUS through tonight. Limited deep convective
potential will be prevalent, with the only potential for
lighting-producing convection expected along the coastal Pacific
Northwest. This is related to an upper low centered off the coasts
of British Columbia and Washington. Low/mid-level lapse rates will
continue to steepen today, particularly across western
Washington/northwest Oregon, where buoyancy may be of sufficient
depth to generate isolated lightning flashes.

$$
--- SBBSecho 3.12-Linux
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ACUS01 KWNS 081930
SWODY1
SPC AC 081928

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0128 PM CST Mon Mar 08 2021

Valid 082000Z - 091200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
A few thunderstorms are possible along the Pacific Coast.

No changes were made to the previous outlook, with only sporadic
lightning possible near the coastal Pacific Northwest.

..Jewell.. 03/08/2021

.PREV DISCUSSION... /ISSUED 1015 AM CST Mon Mar 08 2021/

No changes have been made to the ongoing forecast. A few
thunderstorms may affect coastal areas of OR and northern CA -
mainly tonight. Otherwise, dry and relatively stable conditions
will preclude organized thunderstorm activity.

$$
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ACUS01 KWNS 091928
SWODY1
SPC AC 091927

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0127 PM CST Tue Mar 09 2021

Valid 092000Z - 101200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Widely scattered weak thunderstorm activity is possible today into
tonight near and inland of the Pacific coast, with additional
thunderstorms possible tonight across parts of central and eastern
Nebraska into the Upper Midwest.

No changes were required to the previous outlook.

..Jewell.. 03/09/2021

.PREV DISCUSSION... /ISSUED 1028 AM CST Tue Mar 09 2021/

...Synopsis...
At least a couple of belts of westerlies emanating from the
mid-latitude Pacific appear likely to remain in phase through this
period, with amplified, positively tilted ridging into troughing
across the eastern Pacific into western North America. Within the
troughing, one significant short wave impulse is forecast to dig
sharply south of Yukon through the Canadian Rockies and adjacent
portions of the Canadian Prairies, while a broad and deep mid-level
low digs near and mostly offshore of the Oregon/northern California
coast.

Downstream of the low, broadly cyclone mid-level flow with a number
of embedded short wave perturbations will continue to develop across
and east-northeast of the southern Rockies. Farther north, a couple
of merging impulses are forecast to accelerate northeast of the
central Canadian/U.S. border, around the northwestern periphery of
large-scale mid-level ridging east of the Mississippi Valley.

In lower latitudes, to the east of the ridging, weak mid-level
troughing will continue to gradually shift east of the Bahamas and
Caribbean. As it does, and the center of cool surface ridging
continues to slowly shift east of the south Atlantic Seaboard, some
further boundary-layer moistening is possible across at least the
western Gulf of Mexico. In general, though, this will not yet
become sufficient to support a particularly significant inland
moisture return.

However, within the developing return flow along/east of the higher
terrain of northeastern Mexico through the southern Great Plains,
into parts of the lower Missouri Valley, weak to modest moisture
return is underway beneath relatively warm and capping elevated
mixed-layer air.

...Nebraska into Upper Midwest...
As mid-level flow trends increasingly cyclonic by tonight, an area
of low pressure is forecast to deepen within lee surface troughing
across parts of the central Great Plains. As it does, models
indicate that southerly low-level flow (around 850 mb) will
strengthen in excess of 50 kt by late this evening across parts of
Kansas and Oklahoma into the Iowa vicinity. This is expected to be
accompanied by increasing moisture return (generally above the
boundary layer), and the development of weak potential instability.
Models suggest that this may become sufficient to support scattered thunderstorm development, mainly as the better moisture begins to
underrun the warmer elevated mixed-layer air, generally north of
the Kansas/Nebraska and Missouri/Iowa state border areas. Due to
generally weak shear in the cloud-bearing layer, and weak CAPE, the
potential for severe hail still appears negligible.

...Pacific Coast into northern intermountain region...
Models suggest that stronger mid-level forcing for ascent and
destabilization, and stronger low-level flow, will mostly remain
offshore through this period. However, weak destabilization across
and inland of coastal areas could still become sufficient to support
isolated to widely convection which may briefly become capable of
producing lightning.

$$
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ACUS01 KWNS 101954
SWODY1
SPC AC 101952

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0152 PM CST Wed Mar 10 2021

Valid 102000Z - 111200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM IOWA INTO
SOUTHERN MINNESOTA AND WESTERN WISCONSIN...AND FROM SOUTHEAST KANSAS
INTO WEST-CENTRAL MISSOURI...

...SUMMARY...
A few severe thunderstorms are possible late this afternoon into
this evening across parts of central Iowa into southeastern
Minnesota and adjacent portions of western Wisconsin, and perhaps
this evening into the overnight hours across parts of eastern Kansas
into northwestern Missouri. A tornado is possible across the
northern Slight Risk area.

The previous outlook remains on track with little change necessary.

A ribbon of instability continues to develop ahead of the surface
low into IA, with capping currently in place. Continued heating
should allow for isolated cells to develop east/northeast of the
low, possibly a supercell or two with all hazards possible prior to
cells moving into the cooler air. For more detailed information see
mesoscale discussion 150.

Farther south into MO and southeast KS, additional storms are likely
along the cold front during the evening as convergence increases,
breaking the cap. Hail appears to be the main threat here, as the
boundary layer becomes a bit more stable.

..Jewell.. 03/10/2021

.PREV DISCUSSION... /ISSUED 1029 AM CST Wed Mar 10 2021/

...Synopsis...
Models suggest that broad, positively-tilted mid-level troughing,
within a southern branch of split mid-latitude westerlies, will be
reinforced across the western U.S., as the southwestern portion of a
splitting vigorous short wave trough emerging from the Arctic
latitudes digs southward along the northern Pacific coast. Within
the northern branch, consolidating short wave troughing is forecast
to gradually turn eastward across eastern portions of the Canadian
Prairies. As it does, one significant short wave emerging from the
southern branch troughing is expected to accelerate northeastward
across the middle Missouri Valley through the upper Great Lakes
region by late tonight.

Model spread concerning the lead short wave perturbation and related developments has been sizable. In general, though, guidance appears
to have trended toward stronger associated surface frontal wave
development northeast of the middle Missouri Valley through the
Upper Midwest late this afternoon and evening, along with
intensification of the perturbation through mid-levels. This likely
will be accompanied by considerable intensification of lower/mid
tropospheric wind fields (including 90-100+ kt at 500 mb and 50-70+
kt at 850) within the evolving warm sector of the surface cyclone.
However, low-level moisture return from the western Gulf of Mexico
remains modest to weak, even across the southern Great Plains, and
this will tend to limit destabilization.

...Central Great Plains into Upper Midwest...
Severe weather potential is supported by synoptic forcing and strong
wind fields associated with the developing system, but remains
largely conditioned on sufficient boundary-layer destabilization,
which remains unclear.

Stronger mid/upper support for convective development seems likely
to be largely focused ahead of the short wave impulse, in closer
proximity to the developing surface cyclone across the Upper Midwest
late this afternoon into tonight. However, at least somewhat better
low-level moisture return and associated destabilization will be
focused in the immediate wake of the short wave impulse, as strong
southerly low-level flow persists ahead of the large-scale
Southwestern mid-level troughing.

Severe probabilities across the Upper Midwest have been adjusted a
bit to focus where models now appear in better agreement with the
narrow corridor of stronger pre-frontal boundary-layer warming
across western/central Iowa into southeastern Minnesota (roughly
based on late afternoon model positioning of the 925-850 mb thermal
ridge axis). It appears that surface dew points may increase into
the mid 50s+ F within a narrow corridor near/just east of this axis,
and contribute to at least weak boundary-layer destabilization when
coupled with mid-level cooling. Given the strengthening of the
low-level and deep-layer shear, thermodynamic profiles may become
marginally conducive to supercells, including a risk for tornadoes,
for at least a couple hour period late this afternoon and evening.
Thereafter, a narrow, broken squall line could evolve ahead of the
eastward surging cold front, and continue to pose a risk for strong
wind gusts into this evening, before activity weakens in diminishing instability.

Thunderstorms may develop southward along the front into the central
Great Plains through this evening, as far southwest as the leading
edge of stronger mid-level height rises/capping in the wake of the
short wave impulse. This may be aided by an area of enhanced
lower/mid tropospheric warm advection along/above the surface
frontal zone, across parts of southeastern Kansas into western
Missouri, where a number of stronger storms may pose at least some
risk for severe hail.

$$
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ACUS01 KWNS 111945
SWODY1
SPC AC 111944

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0144 PM CST Thu Mar 11 2021

Valid 112000Z - 121200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE OHIO
VALLEY WESTWARD INTO THE OZARKS AND PLAINS...

...SUMMARY...
Strong thunderstorm activity may impact a corridor across the Ozark
Plateau through the Ohio Valley today, posing some risk for
potentially damaging wind gusts. Tonight strong thunderstorms may
develop in a corridor across the Ozark Plateau through the south
central Great Plains and pose some risk for severe hail.

Little change was made to the previous outlook. For more information
on MO/IL/IN parts of the Marginal Risk, see mesoscale discussion
154.

..Jewell.. 03/11/2021

.PREV DISCUSSION... /ISSUED 1028 AM CST Thu Mar 11 2021/

...Synopsis...
Low-amplitude mid-level ridging, within the northern branch of split
westerlies emanating from the mid-latitude Pacific, is shifting
inland of the British Columbia coast and forecast to develop
eastward across the Canadian Prairies by late tonight. This will
occur in the wake of one vigorous short wave trough digging
east-southeast of the Canadian Prairies through Ontario. A vigorous
preceding short wave impulse (which emerged from the upstream
southern branch troughing) is already accelerating northeast and
east of the Great Lakes region, and may approach the Canadian
Maritimes by 12Z Friday.

A deep surface cyclone accompanying the lead short wave trough
appears likely to rapidly migrate across southeastern Ontario
through Quebec, with a trailing cold front advancing eastward across
the lower Great Lakes, Ohio Valley and much of the Northeast.
Models suggest that the trailing southwestern flank of the surface
front will stall across the Ozark Plateau through the Texas/Oklahoma
Panhandle region, beneath building ridging within the southern
branch of the westerlies, to the north of an increasingly prominent
subtropical high centered over the Gulf of Mexico.

This ridging is forecast to build ahead of a vigorous short wave
impulse pivoting around the southern periphery of a broad southern
branch closed low. While the center of the mid-level low may
redevelop southeastward from central through southern California,
models indicate only a very slow eastward progression of surrounding larger-scale positively tilted troughing. The mid-level cold core
of the aforementioned vigorous short wave impulse may remain largely
offshore of the southern California coast through this period.

Significant low-level moistening off a still modifying western Gulf
of Mexico boundary layer has been, and remains, slow to develop.
While further moistening is possible today through tonight, the most substantive surface dew points (upper 50s through mid 60s F) appear
likely to remain focused beneath warming and more strongly capping
mid-level layers across the southern Great Plains and lower
Mississippi Valley vicinity. Still, moistening may contribute to
sufficient destabilization to support at least low probabilities for thunderstorms across the lower Great Lakes/upper Ohio Valley and
adjacent portions of the Northeast. Highest thunderstorm
probabilities will remain focused along the
stalling/quasi-stationary frontal zone across the lower Ohio Valley
into the south central Great Plains.

...Ozark Plateau into Ohio Valley today...
Destabilization along/just ahead of the surface frontal zone likely
will remain weak. However, aided by some further moistening, in the
presence of 30-50+ kt westerly lower/mid tropospheric wind fields, precipitation loading and downward mixing of higher momentum may
contribute to at least some risk for locally damaging wind gusts in
stronger convection this afternoon and evening.

...Ozark Plateau into Ohio Valley tonight...
While the surface front may remain stalled, the baroclinic zone in
lower to mid-levels may retreat slowly northward overnight, while
also becoming a focus for scattered, but increasing, thunderstorm
development. Aided by modestly steep mid-level lapse rates and
cloud-bearing layer shear, it is possible that a few of the stronger
cells could pose a risk for severe hail.

$$
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ACUS01 KWNS 131232
SWODY1
SPC AC 131231

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0631 AM CST Sat Mar 13 2021

Valid 131300Z - 141200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS THIS
AFTERNOON/EVENING ACROSS THE EAST CENTRAL AND SOUTHEAST TX
PANHANDLE...

...SUMMARY...
Scattered to numerous severe storms are expected later today into
early tonight from west Texas into western Oklahoma and southwestern
Kansas. The most significant severe weather threat, including
strong tornadoes and very large hail, is expected this
afternoon/evening across the east central and southeast Texas
Panhandle.

...Southern High Plains through early tonight...
A deep closed low over AZ will progress eastward to the southern
High Plains by the end of the period. In association with an
embedded jet streak rotating northeastward around the eastern
periphery of the low, a surface cyclone will develop
north-northeastward from the TX Panhandle this afternoon to
southwestern KS tonight. The cyclogenesis will draw the surface
warm sector northward across western OK and the TX Panhandle today
to the east of a developing dryline, which will focus severe storm
development this afternoon/evening.

Some elevated convection is expected this morning from northeast NM northeastward into southwest KS, within the exit region of the
mid-upper jet. Midlevel lapse rates/buoyancy will be sufficient for
isolated large hail with this convection. Farther southeast and
following a lull in the overnight convection, the warm sector will
spread northward today, beneath midlevel lapse rates greater than 8
C/km. Moderate buoyancy (MLCAPE of 1500-2000 J/kg) is expected
south of the warm front and east of the dryline this afternoon, with
only weak convective inhibition along the dryline. Initial storm
development is expected early-mid afternoon along the dryline in the
vicinity of I-27 in TX Panhandle/South Plains. These initial storms
will move off the dryline and maintain more discrete character as
they encounter a moist, destabilizing warm sector with strong
vertical shear. Given boundary-layer dewpoints in the low 60s,
afternoon temperatures of 65-70 F, effective bulk shear near 70 kt,
and effective SRH in excess of 250 m2/s2, there will be a few hour
window for a couple of supercells to produce long-track, strong
tornadoes and very large hail across the east central/southeast TX
Panhandle.

West of the initial supercells, squall line development is expected
by evening as a Pacific cold front overtakes the dryline and the
stronger height falls/ascent overspread the TX Panhandle and west
central TX. Embedded supercell structures within the line will be
capable of producing all hazards, though the overall severe threat
will weaken with eastward extent during the early overnight hours,
as a result of diminishing buoyancy.

..Thompson/Gleason.. 03/13/2021

$$
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ACUS01 KWNS 131942
SWODY1
SPC AC 131940

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0140 PM CST Sat Mar 13 2021

Valid 132000Z - 141200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON AND EVENING ACROSS PARTS OF THE EASTERN TEXAS PANHANDLE...

...SUMMARY...
Numerous severe storms are expected late this afternoon into tonight
across west Texas into western Oklahoma and southwestern Kansas. The
most significant severe weather threat, including the potential for
long-lived supercells capable of producing strong tornadoes is
expected across the eastern Texas Panhandle into portions of the
Texas Big Country through early evening.

...20Z Outlook Update...
Slight adjustments have been made to the categorical and
probabilistic lines, mainly to account for the progression of
synoptic features and associated destabilization.

A narrow corridor of moderate boundary-layer destabilization along
and just ahead of an eastward advancing dryline still appears likely
to become the focus for considerable intense thunderstorm
development late this afternoon and evening across western Texas.
Southerly low-level jet strengthening (40-60 kt around 850 mb)
forecast across parts of the Texas Big Country into the eastern
Texas Panhandle will contribute to substantive further enlargement
of clockwise-curved low-level hodographs by around 00-01Z, along
with a corresponding increase in convective organization and peak in
severe weather potential early this evening.

..Kerr.. 03/13/2021

.PREV DISCUSSION... /ISSUED 1029 AM CST Sat Mar 13 2021/

...Southern High Plains...
No change to the long-track/strong tornado threat driving the MDT in
the eastern TX Panhandle. Primary changes this update are to add a
30 SIG wind area across a portion of western north TX, expand the 5
tor area south along the dryline into the Edwards Plateau region,
and broaden the western gradient of the threat probabilities for a
potentially slower dryline evolution with initial afternoon
development.

A deep closed low near the AZ/UT border will progress east across
the southern Rockies through the end of the period. In association
with an embedded jet streak rotating northeastward around the
eastern periphery of the low, a surface cyclone will deepen as it
ejects north-northeast across the TX Panhandle this afternoon into
southwest KS tonight. The cyclogenesis will draw the surface
warm sector northward across western OK and the TX Panhandle to the
east of a developing dryline, which will focus severe storm
development this afternoon/evening.

Regenerative elevated convection has persisted this morning from
northeast NM northeastward into southwest KS, within the exit region
of the mid-upper jet. Mid-level lapse rates/buoyancy will be
sufficient for a threat of isolated severe hail. Farther south, the
warm sector will spread north today, beneath very steep mid-level
lapse rates of 8-9 C/km. Greater boundary-layer heating is expected
initially from the TX South Plains south, before spreading north
towards late afternoon. A plume of moderate buoyancy with MLCAPE of
1500-2000 J/kg is expected south of the warm front and east of the
dryline at peak heating.

Initial surface-based storm development is expected by early-mid
afternoon along the dryline in the vicinity of I-27 in the TX
Panhandle. These initial storms will move off the dryline and
maintain more discrete character as they encounter a moist,
destabilizing warm sector with strong vertical shear. Given
boundary-layer dewpoints in the low 60s, afternoon temperatures in
the upper 60s to lower 70s, effective bulk shear near 70 kt, and
effective SRH in excess of 250 m2/s2, there will be a few hour
window for a couple of supercells to produce long-track, strong
tornadoes and very large hail centered on the east central/southeast
TX Panhandle.

To the west and south of the discrete supercells, squall line
development is expected by early evening as a Pacific cold front
overtakes the dryline and the stronger height falls/ascent
overspread northwest to west-central TX. Embedded supercell
structures within the line will be capable of producing all hazards.
Effective bulk shear in excess of 60 kt will also support a few hour
window for bowing structures. With 50-60 kt 700-mb flow expected
both ahead of and behind the squall, along with pronounced surging
of the Pacific front, a threat for significant severe wind gusts may
be realized as well. The overall severe threat should largely weaken
with eastward extent during late evening to early overnight as a
result of diminishing buoyancy in western OK towards central
portions of TX.

$$
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ACUS01 KWNS 141227
SWODY1
SPC AC 141226

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0726 AM CDT Sun Mar 14 2021

Valid 141300Z - 151200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
INTO EARLY TONIGHT FOR PARTS OF NORTHWEST/NORTH CENTRAL KS AND
EASTERN AR AND VICINITY...

...SUMMARY...
Isolated strong-severe storms will be possible later this afternoon
into early tonight across northwest/north central Kansas and across
eastern Arkansas and vicinity.

...Synopsis...
A deep, occluded low over the High Plains of eastern CO/western KS
will slowly weaken and drift eastward today. An embedded mid-upper
jet streak will rotate around the southeastern periphery of the low,
in conjunction with an eastward surging cold front from OK/TX this
morning to AR/LA this afternoon/evening. Only weak convection has
been noted overnight in the band of ascent with the cold front, and
this should continue into the first half of the day as a result of
very marginal buoyancy in the warm sector, as well as the notable
cap near 700 mb in 12z soundings from CRP-SHV-LZK. There is some
chance for modest surface heating and a little increase in low-level
moisture from LA into AR ahead of the front this afternoon into this
evening, and a resultant small increase in buoyancy as ascent erodes
the midlevel stable layer. If destabilization is sufficient (at
least a few hundred J/kg of SBCAPE), then a conditional threat for
isolated damaging gusts and an isolated tornado could be realized
with the frontal convection this afternoon into early tonight, given substantial vertical shear.

Otherwise, a second area of surface-based convection will be
possible this afternoon/evening across KS, near the triple point of
the dry slot and the north edge of the warm sector. Here, surface
heating beneath cold midlevel temperatures will result in steep
lapse rates and the potential for low-topped storms with isolated
large hail, mainly this afternoon/evening.

..Thompson/Gleason.. 03/14/2021

$$
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ACUS01 KWNS 141952
SWODY1
SPC AC 141951

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0251 PM CDT Sun Mar 14 2021

Valid 142000Z - 151200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THROUGH THIS
EVENING FROM NORTHEAST CO INTO NORTHWEST KS AND SOUTHWEST NE...AND
LATER TONIGHT ACROSS PARTS OF THE LOWER MS VALLEY...

...SUMMARY...
Isolated severe thunderstorms are possible across a part of
northeast Colorado, northwest Kansas and southwest Nebraska through
early evening, and across a portion of the Lower Mississippi Valley
tonight.

...20z Update - CO/KS/NE...

The Marginal risk area has been shifted west/southwest this
afternoon. This is based on current surface observations and visible
satellite imagery. A surface low is located north of LAA and
southwest of ITR with an occluded front extending from the low
north/northeast a near the KS/NE border. Strong surface heating in
the vicinity of this boundary has resulted in weak destabilization
this afternoon and isolated thunderstorms have developed along the
boundary and near the surface low. Marginal hail will be possible
with this activity given steep midlevel lapse rates and moderate
shear. Low level shear will remain enhanced near the boundary, and a
funnel cloud has already been reported with a cell in Hitchcock
County NE. Brief funnels or even a weak tornado will remain possible
the next few hours. For more details, reference MCD 177.

Otherwise, the remainder of the outlook remains on track and no
other changes were made except to adjust 10% general thunder in line
with current observations.

..Leitman.. 03/14/2021

.PREV DISCUSSION... /ISSUED 1122 AM CDT Sun Mar 14 2021/

...Lower MS Valley...
A deep, occluded low over eastern CO will slowly fill as it drifts
east into western KS through tonight. An embedded mid-upper jet
streak will rotate around the southeastern periphery of the low,
in conjunction with a Pacific cold front moving from eastern OK/TX
into AR/LA by this evening. Only meager convection has been noted
this morning in the band of ascent along and behind the front. This
may continue through much of the period as a result of paltry
warm-sector buoyancy, as well as a capping inversion around 700 mb
in 12Z soundings from CRP-SHV-LZK. Still, conditional potential for
a tornado or isolated strong wind gust exists tonight as mid 60s
surface dew points spread toward the Ark-La-Miss and mid-level temps
slightly cool. This may result in a small corridor of spatiotemporal
overlap with 250-500 J/kg MLCAPE and a moderately enlarged low-level
hodograph.

...Northwest/north-central KS to southwest NE...
A narrow corridor of low-topped surface-based convection might
develop during the late afternoon to early evening along a
convergent occluded front where a plume of 40s surface dew points
can be maintained. Here, surface heating beneath rather cold
mid-level temperatures should result in steep low to mid-level lapse
rates. Low probabilities are maintained for marginally severe hail
along with a brief tornado from a cell or two.

$$
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ACUS01 KWNS 151950
SWODY1
SPC AC 151949

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0249 PM CDT Mon Mar 15 2021

Valid 152000Z - 161200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE LOWER
MO VALLEY AND MS/AL...

...SUMMARY...
Isolated severe storms are possible across parts of Alabama and
Mississippi through tonight. Isolated severe storms are also
possible from east-central Kansas through central Missouri through
early evening.

...20z Update...

The ongoing outlook remains on track and no changes are needed with
this update. Reference MCD 180 for short-term severe threat across
MS/AL, and MCD 181 for the short-term severe threat across KS/MO.

..Leitman.. 03/15/2021

.PREV DISCUSSION... /ISSUED 1130 AM CDT Mon Mar 15 2021/

...MS/AL...
A low-confidence severe threat remains apparent across the region
through tonight. A band of predominantly low-topped showers is
ongoing from northwest AL to southwest MS along a weakening surface
cold front, to the south of an embedded shortwave impulse advancing
north across the Mid-MS Valley. While further frontolysis is
expected, some of this convective activity should persist through
the afternoon and become more west/east-oriented across
northern/central AL and central MS. Broken cloudiness out ahead of
this activity will support further boundary-layer heating amid mid
60s dew points from the western half of AL to the southwest.
Low-level wind profiles should slowly weaken and become more veered
with western extent. The conditional threat for a supercell or two
during the late afternoon to early evening may be focused across the west-central AL vicinity where all hazards would be possible. Still,
given the poor forcing for large-scale ascent, probabilities remain
too low to warrant an upgrade this outlook. Otherwise, additional
convection may form overnight within a weak low-level warm advection
regime to the north of the central Gulf Coast. Rich low-level
moisture and continued strong deep-layer shear may support a
low-probability severe threat.

...East-central KS to central MO...
The deep closed low over central KS will evolve into an open wave
and eject east-northeast across the Midwest through tonight, in
response to upstream height falls with a strong shortwave trough
digging across CA. Though the richer low-level moisture is confined
to the Lower MS Valley, lingering boundary-layer dewpoints in the
mid to upper 40s are prevalent within the northern extent of robust
insolation across southeast KS and southwest MO. Beneath cold
mid-level temperatures, the steep-lapse-rate environment will
support meager MLCAPE approaching 500 J/kg in a corridor east of the
surface cyclone and along a stalled front in central MO.

Within the left-exit region of a strengthening mid-level jet,
isolated to scattered thunderstorms are expected to form by mid
afternoon in the zone of ascent near/east of the surface low towards
the KS/MO border, with successive development of storms eastward
into central MO through early evening. Wind profiles, especially
with eastern extent in central MO, should support a couple
low-topped supercells with effective bulk shear of at least 30 kt
and some hodograph curvature in the low levels. Marginally severe
hail, isolated damaging gusts, and a tornado will be possible with
storms along the boundary this afternoon/evening. The bulk of
convection should generally propagate further across the cool side
of the front, where low-level stratus will likely remain pervasive,
and become elevated before weakening later this evening.

$$
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ACUS01 KWNS 161629
SWODY1
SPC AC 161628

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1128 AM CDT Tue Mar 16 2021

Valid 161630Z - 171200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS NORTHWEST AND NORTH-CENTRAL OK...

...SUMMARY...
Scattered severe storms with large hail (some significant), damaging
winds, and a few tornadoes are expected tonight across the southern
Great Plains to the Ark-La-Miss. Isolated severe storms will also be
possible from southern Mississippi to central Georgia through this
evening.

...Central/southern portions of MS/AL/GA to
Ark-La-Tex/Ark-La-Miss...
A cluster of non-severe convection persists across a swath of
central AL to southern MS. The predominant WSW-ENE orientation and
attendant anvil shading will limit stronger boundary-layer heating
to the south of this convection to the Gulf Coast. This activity
will likely continue through this afternoon into the evening, along
the northern/northeastern MLCAPE gradient. The orientation of the
clusters generally oriented parallel to the deep-layer shear vector
should be a limiting factor despite 40-50 kt effective shear.
Effective SRH of 100-150 m2/s2 is expected to persist and may
support a few transient, low-end supercell structures from southern
MS to the stationary front in central GA. Isolated damaging
winds/severe hail and a tornado or two will all be possible.

Closer to the Ark-La-Tex and Lower MS Valley, a confluence axis
currently trails from the ongoing clusters and should advance north. Strengthening low-level warm advection after sunset should aid in at
least isolated discrete cells developing near this confluence axis.
Mid-upper 60s boundary-layer dewpoints and only weak convective
inhibition suggest that storms will maintain surface-based inflow
parcels with a threat of all hazards. The cat 2/SLGT risk has been
expanded to account for this scenario.

...Southern Great Plains to the Lower MS Valley...
A compact, deep mid-level low over central AZ will progress east,
reaching the TX Panhandle overnight. Lee cyclogenesis is expected
this afternoon near the NM/TX border, and the surface cyclone will
move into west-central OK overnight. In advance of the cyclone,
low-level moisture (boundary-layer dewpoints in the mid-upper 60s)
will surge northward from south TX and LA to southern portions of
OK/AR tonight on strengthening southerly low-level flow. This
moistening will occur beneath a broad plume of steepening mid-level
lapse rates between 8-9 C/km, yielding MUCAPE of 2000-3000 J/kg
overnight.

The boundary layer will be capped through the day, but continued destabilization and the approach of strong height falls/ascent from
the west will likely support thunderstorm development by late
evening from the eastern TX Panhandle into western OK and southern
KS. The storms closer to KS will likely remain elevated north of the
warm front, though wind profiles will favor several elevated
supercells capable of mainly producing large hail, with isolated
severe gusts still possible. Farther south in OK, storms should be
rooted near the surface, with deep-layer shear and buoyancy
favorable for supercells with very large hail. Wind profiles will
also be sufficient for some tornado threat, though uncertainty
exists regarding storm mode/coverage with southward extent late in
the period.

Thunderstorm development will also be possible late tonight in
west-central TX as a Pacific cold front overtakes the dryline over
the Edwards Plateau. The frontal storms will move east and may
develop northeast as well, posing a risk for mainly large hail and
damaging wind gusts into central and north-central TX during the
early morning.

..Grams/Bentley.. 03/16/2021

$$
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ACUS01 KWNS 172139
SWODY1
SPC AC 172137

Day 1 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
0437 PM CDT Wed Mar 17 2021

Valid 172000Z - 181200Z

...THERE IS A HIGH RISK OF SEVERE THUNDERSTORMS ACROSS ALABAMA...MISSISSIPPI...FAR NORTHEAST LOUISIANA AND FAR SOUTHEAST
ARKANSAS...

CORRECTED TO CHANGE I-80 TO HIGHWAY-80

...SUMMARY...
A significant tornado outbreak is expected with numerous strong and
a few long-track, potentially violent tornadoes. The initial round
will continue across Alabama this afternoon. A separate swath should
emanate from far northeast Louisiana this afternoon and spread east
across Mississippi and Alabama this evening into tonight.

...DISCUSSION...
A few changes have been made to the outlook for this issuance. The
first change is to move the High Risk area southward to include more
of south-central Mississippi and southwest Alabama. The 45 percent
contour has also been adjusted southward, to encompass the first
phase of the tornado outbreak ongoing in southwest Alabama. The
newest tornado outbreak model guidance places the greatest threat
along a corridor east-northeast from near Jackson, Mississippi
east-northeast along the Highway-80 corridor into the area to the
south of Tuscaloosa, Alabama.

The second is to extend the slight risk westward into parts of
northeast Oklahoma. Severe thunderstorms are ongoing and will spread
northward across northeast Oklahoma this afternoon. Wind damage,
isolated large hail and a tornado or two will be possible with these
storms.

The third change is to remove the enhanced risk from southwest
Missouri. Severe thunderstorms are developing in northeast Oklahoma
and it appears, that the distribution of reports will be over a
broader area and more isolated than previously thought.

..Broyles.. 03/17/2021

.PREV DISCUSSION... /ISSUED 1106 AM CDT Wed Mar 17 2021/

...Deep South...
Minor change made to the categorical HIGH risk area to expand a bit.
Main change is to the underlying probabilities with the addition of
a 45 tor and 45 wind. A dangerous, long-duration tornado outbreak
expected to commence this afternoon and persist well into tonight
with multiple rounds of heightened tornado potential.

Ongoing convection is within an arc with a pre-frontal squall from
far east TX to northeast AR and then in a more west/east-orientation
from northeast AR to the AL/TN border area. The northern activity
will tend to reinforce the surface warm front approaching the TN
border with MS/AL this afternoon. The southwest band will likely
persist east and should breakup into a broken band of supercells at
some point this afternoon as low-level shear further strengthens
across the Ark-La-Miss region. Farther east, warm-advection showers
in southeast MS to west-central AL will likely deepen by early
afternoon into a separate swath of several discrete supercells in an environment of strengthening low to deep-layer shear. Between these
two areas, the destabilizing warm sector with warming boundary-layer temperatures and mid 60s to low 70s dew points, will support an
expansive plume of 1500-2500 J/kg MLCAPE.

By late afternoon and into early tonight, a low-level jet segment
will strengthen to at least 50-60 kt across MS/AL as the midlevel
trough approaches from the west, contributing to very strong
low-level shear (0-1 km SRH in excess of 300 m2/s2). Buoyancy will
be slow to decrease after sunset and with eastward extent based on
the prevalence of rather rich boundary-layer dew points, Very
favorable wind profiles (with 700-mb winds reaching 70-80 kt) will
maintain the threat for long-track, intense tornadoes with both
warm-sector supercells, as well as supercells within the broken band
near and ahead of the surface wind shift progressing east across MS
by early tonight. The strong tornado and significant damaging wind
threat while becoming more spatially confined with time, will likely
persist across parts of AL overnight and should spread into western
GA before 12Z.

$$
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ACUS01 KWNS 181635
SWODY1
SPC AC 181633

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1133 AM CDT Thu Mar 18 2021

Valid 181630Z - 191200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS CENTERED ON THE
CENTRAL AND EASTERN CAROLINAS...

...SUMMARY...
Scattered severe thunderstorms will likely be centered on the
central and eastern Carolinas. A few tornadoes (a couple of which
might be strong), damaging winds, and some hail remain possible.
Other isolated severe storms are possible from southern Ohio into
the central Appalachians, and across north Florida.

...Southeast...
Overall severe threat will likely focus in two corridors which are
encompassed by the cat 3/ENH risk for tornado and wind. Initial
broken band of non-severe convection is ongoing from south-central
GA through the eastern FL Panhandle. This activity has struggled to
intensify despite strong low to deep-layer shear as it impinges on a
relative minimum in buoyancy sampled by the 12Z JAX sounding and
evident in mesoanalysis time-series. However, destabilization is
occurring downstream from north FL to the coastal Carolinas and
redevelopment of severe storms is anticipated at some point this
afternoon. The eastward translation of a 50-55 kt LLJ will support
an enlarged hodograph favorable for a few supercells. Modest
mid-level lapse rates will remain a limiting factor, though MLCAPE
will be large enough given to support a few tornadoes and scattered
damaging winds, with a strong tornado or two still possible.

The separate area of potential severe should be coincident with the
track of a mesolow from the northeast GA/northwest SC border across
the Piedmont towards south-central VA. Here, MLCAPE will likely
remain weak but cloud breaks just ahead of the low near the
mid-level dry slot may prove sufficient for an intensifying area of
convection. Where sufficient buoyancy overlaps the more
favorable/curved hodographs east of the mountains, a couple
supercells capable of a strong tornado, damaging winds, and isolated
large hail will all be possible this afternoon/evening.

...OH Valley...
East and southeast of the weakening occluded cyclone, pockets of
stronger boundary-layer heating are underway on the nose of the
mid-level dry slot. In conjunction with cool mid-level temperatures,
500-1000 J/kg of MLCAPE will be sufficient for a few strong-severe
storms later this afternoon. This area will be on the northwest edge
of the stronger flow/shear, where a mix of multicell clusters and a
few low-end supercells are probable. A tornado or two, large hail,
and damaging winds will be possible.

..Grams/Broyles.. 03/18/2021

$$
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ACUS01 KWNS 182127
SWODY1
SPC AC 182126

Day 1 Convective Outlook AMEND 1
NWS Storm Prediction Center Norman OK
0426 PM CDT Thu Mar 18 2021

Valid 182000Z - 191200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHERN
SOUTH CAROLINA THROUGH CENTRAL AND EASTERN NORTH CAROLINA AND
SOUTHEAST VIRGINIA...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER THE SOUTHERN APPALACHIANS AND A PORTION OF NORTHERN FLORIDA...

AMENDED FOR TO EXPAND ENHANCED RISK FARTHER NORTH INTO SOUTHEAST
VIRGINIA FOR TORNADO AND DAMAGING WIND THREAT

...SUMMARY...
Scattered severe storms remain possible this afternoon and evening
mainly from a portion of South Carolina through central and eastern
North Carolina and southeast Virginia. Other strong to severe storms
are possible this afternoon over the southern Appalachian region as
well as northern Florida.

...South Carolina through central and eastern North Carolina and
southeast Virginia...

Cluster of storms over western SC and southwestern NC is expected to
continue developing northeast through central and eventually eastern
NC this afternoon and evening. Vertical wind profiles with 50+ kt
effective bulk shear and sizeable 0-2 km hodographs will remain
supportive of organized severe storms including supercells. However,
trend has been for a pocket of dry air in the low levels to advect
northward through northern SC into southeastern NC, and this has at
least temporarily reduced boundary layer instability. Nevertheless,
some low-level theta-e advection will resume in wake of the dry
pocket contributing to 1000-1500 J/kg MLCAPE. The best chance for
severe storms are expected as activity develops northeast along
instability gradient through a portion of central and eastern NC and
possibly southeast VA this afternoon and evening with damaging wind,
large hail and a few tornadoes possible.

...Southern Appalachian region...

Storms are developing within corridor of ascent just east of the
progressive shortwave trough. Cold temperatures aloft, steep lapse
rates and diabatic heating will continue to foster widely scattered
storm development this afternoon. Isolated large hail and a few
locally strong wind gusts are the main threats. Activity should
diminish toward late afternoon or early evening.

..Dial.. 03/18/2021

.PREV DISCUSSION... /ISSUED 1133 AM CDT Thu Mar 18 2021/

...Southeast...
Overall severe threat will likely focus in two corridors which are
encompassed by the cat 3/ENH risk for tornado and wind. Initial
broken band of non-severe convection is ongoing from south-central
GA through the eastern FL Panhandle. This activity has struggled to
intensify despite strong low to deep-layer shear as it impinges on a
relative minimum in buoyancy sampled by the 12Z JAX sounding and
evident in mesoanalysis time-series. However, destabilization is
occurring downstream from north FL to the coastal Carolinas and
redevelopment of severe storms is anticipated at some point this
afternoon. The eastward translation of a 50-55 kt LLJ will support
an enlarged hodograph favorable for a few supercells. Modest
mid-level lapse rates will remain a limiting factor, though MLCAPE
will be large enough given to support a few tornadoes and scattered
damaging winds, with a strong tornado or two still possible.

The separate area of potential severe should be coincident with the
track of a mesolow from the northeast GA/northwest SC border across
the Piedmont towards south-central VA. Here, MLCAPE will likely
remain weak but cloud breaks just ahead of the low near the
mid-level dry slot may prove sufficient for an intensifying area of
convection. Where sufficient buoyancy overlaps the more
favorable/curved hodographs east of the mountains, a couple
supercells capable of a strong tornado, damaging winds, and isolated
large hail will all be possible this afternoon/evening.

...OH Valley...
East and southeast of the weakening occluded cyclone, pockets of
stronger boundary-layer heating are underway on the nose of the
mid-level dry slot. In conjunction with cool mid-level temperatures,
500-1000 J/kg of MLCAPE will be sufficient for a few strong-severe
storms later this afternoon. This area will be on the northwest edge
of the stronger flow/shear, where a mix of multicell clusters and a
few low-end supercells are probable. A tornado or two, large hail,
and damaging winds will be possible.

$$
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ACUS01 KWNS 191938
SWODY1
SPC AC 191937

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0237 PM CDT Fri Mar 19 2021

Valid 192000Z - 201200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
No areas of severe thunderstorms are forecast today.

...20Z Update...
Only change needed to the ongoing forecast was a minor expansion to
include a bit more of south-central/southwest ID where sporadic
lightning has been observed over the last hour. No other changes
were needed to the previous outlook.

..Mosier.. 03/19/2021

.PREV DISCUSSION... /ISSUED 1126 AM CDT Fri Mar 19 2021/

...OR/WA...
A deep upper low is present today of the WA/OR coast. This system
will weaken and slowly approach the coast tonight. Radar and
satellite imagery show bands of showers and thunderstorms
immediately offshore. Several of these cells have produced
lightning, and a few have shown low-level rotation as they moved
onto land. This convection is very shallow, and in a region with
CAPE values of only 0-250 J/kg. Nevertheless, very cold
temperatures aloft and terrain effects may result in a brief spin-up
or two along the immediate coastline. Present indications are that
the overall severe threat appears too low to introduce probabilities
at this time.

Elsewhere, isolated thunderstorms may affect portions of MT, ID, and
far south FL this afternoon. No severe storms are expected in these
areas.

$$
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ACUS01 KWNS 201229
SWODY1
SPC AC 201228

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0728 AM CDT Sat Mar 20 2021

Valid 201300Z - 211200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunder is possible from portions of the eastern Great
Basin to the northern Rockies.

...Synopsis/Discussion...
In mid/upper levels, a high-amplitude synoptic trough will progress
eastward from its current position over the West Coast States and
BC. It southern portion will lag, related to shortwave activity
around the base, while the northern portion crosses AB and the
northern U.S. Rockies tonight. By 12Z, the trough should extend
across western SK, central MT, central NV, and central CA, then for
well over 1000 miles west-southwestward across the northeastern
Pacific. Related height falls, pulses of shortwave-related DCVA
aloft, and a low-level frontal zone will impinge on marginal
low/middle-level moisture today. Sufficient lift and marginal
buoyancy (up to about 200 J/kg total MUCAPE), extending into lightning-supporting thermal layers, may exist for isolated thunder
from portions of the Great Basin to central/western WY.

Elsewhere, a split-flow pattern will amplify over the eastern CONUS,
with a slowly eastward-drifting/southern-stream trough extending
from the southern Appalachians region to the north-central/
northeastern Gulf. Although north of a prior low-level frontal
passage, thunder potential will increase from this afternoon into
tonight over Atlantic waters offshore from SC, GA and northern/
central FL. Large-scale mid/upper-level cooling ahead of the trough
-- and above an area of favorable marine heat/moisture fluxes --
will lead to deepening and increasing deep-layer buoyancy. However,
most (if not all) of the associated lightning-producing convection
should remain over the Atlantic, and because of weak instability,
thunder potential currently appears too low with activity moving
inland for an unconditional outlook area.

..Edwards.. 03/20/2021

$$
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ACUS01 KWNS 201919
SWODY1
SPC AC 201918

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0218 PM CDT Sat Mar 20 2021

Valid 202000Z - 211200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunder is possible from portions of the eastern Great
Basin to the northern Rockies.

Little change was made to the previous outlook with only isolated,
non-severe thunderstorms expected over the Great Basin into Wyoming.
Weak instability will be the mitigating factor despite favorable
lift and strong deep-layer shear.

..Jewell.. 03/20/2021

.PREV DISCUSSION... /ISSUED 1115 AM CDT Sat Mar 20 2021/

No changes have been made to the ongoing thunderstorm forecast.
Occasional lightning flashes are possible through this afternoon and
tonight across portions of the Great Basin and northern Rockies,
ahead of an upper trough over the Pacific Northwest. Some
consideration was given to adding thunderstorm probabilities to
portions of northern ID and northwest MT. However, very limited
moisture and weak updrafts may preclude charge separation.

$$
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ACUS01 KWNS 211221
SWODY1
SPC AC 211220

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0720 AM CDT Sun Mar 21 2021

Valid 211300Z - 221200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are possible tonight over western/central Kansas and
small parts of adjacent states.

...Synopsis...
In mid/upper levels, a progressive synoptic pattern is forecast
through the period. The persistent trough over the southeastern
CONUS -- initially located from the central/southern Appalachians to
the northern gulf -- will move offshore over the Atlantic. While an
isolated lightning flash cannot be ruled out with associated
convection over land, the great majority of thunderstorms (and
coverage above 10%) will remain over Atlantic waters.

Farther west, a positively tilted trough was apparent in moisture-
channel imagery from central MT across central NV and central CA,
then well west-southwestward over the northeastern Pacific. This
trough is expected to split into northern- and southern-stream
members during the period, as the MT portion (and its extension now
northward over SK) move more rapidly eastward. The southern portion
-- with vorticity maxima initially near the ID/NV/UT border
confluence and near coastal central CA -- will dig southeastward
through the period. By 12Z tomorrow, phasing in the southern stream
will yield a closed 500-mb cyclone over the Four Corners region.

At the surface, 11Z analysis showed a wavy cold front from southern
MB across the eastern Dakotas, central/southwestern NE, and
northeastern CO. A lee trough was drawn from northeastern CO south-southwestward over northeastern/east-central NM. A coherent
surface low should develop by this evening over northeastern NM,
then shift slowly eastward over the TX Panhandle, becoming attached
to the southward-moving front. By 12Z, the low should be located
near AMA, with front northeastward to central/northeastern KS and
central IA, and arching across east-central/north-central NM.

...Central Great Plains...
Intensification of the NM lee/frontal cyclone from late afternoon
onward will strengthen mass response and moist advection/transport
within a low-level warm-advection regime already in place across the southern/central Plains. This should include development of a
45-55-kt LLJ tonight over portions of the TX/OK Panhandles, western
OK and central/western KS. Isentropic lift of increasingly moist/higher-theta-e parcels to LFC will occur. Buoyancy will be
modest -- with time series of forecast soundings showing MUCAPE only
reaching the 100-500 J/kg range - but sporadically extending into
thermal layers suitable for lightning production. Thunder potential
should begin around 02Z over western/northern parts of the outlook
area, then expand/shift eastward through the overnight hours, with
some southward backbuilding possible toward southern KS late.

..Edwards.. 03/21/2021

$$
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ACUS01 KWNS 211920
SWODY1
SPC AC 211919

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0219 PM CDT Sun Mar 21 2021

Valid 212000Z - 221200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are possible tonight over western/central Kansas and
small parts of adjacent states.

A few elevated thunderstorms are expected this evening and overnight
across parts of the central Plains as large-scale ascent increases
in advance of a shortwave trough over the Four Corners. Severe
weather is unlikely given weak instability.

Elsewhere, isolated lightning flashes are likely to wane over
southeastern GA today as the upper trough slowly departs.

..Jewell.. 03/21/2021

.PREV DISCUSSION... /ISSUED 1127 AM CDT Sun Mar 21 2021/

...1630z Discussion...

Earlier thoughts regarding the potential for convection remain
across the central Plains region. Upper troughing over the
southwestern US will shift east into the southern Rockies late
tonight. High-level diffluent flow aloft will overspread this region
into KS as low-level warm advection focuses along/north of a frontal
zone that will drape itself across central KS-OK Panhandle-northeast
NM. Elevated buoyancy will likely be adequate for a few
thunderstorms within this zone of large-scale forcing.

Isolated thunderstorms have developed a bit farther west than
earlier anticipated near the GA Coast. Strong easterly low-level
warm advection appears to be the primary mechanism for isolated
thunderstorms across southeast GA late this morning. Forecast
soundings suggest elevated storms may linger into the mid afternoon
hours.

$$
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ACUS01 KWNS 231619
SWODY1
SPC AC 231617

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1117 AM CDT Tue Mar 23 2021

Valid 231630Z - 241200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
OVER PORTIONS OF SOUTHEAST LOUISIANA...

...SUMMARY...
Isolated severe thunderstorms may impact parts of the lower Delta
region and lower Missouri to mid Mississippi Valleys.

...LA/MS...
A line of thunderstorms currently extends from central MS
southwestward to the LA coast. Several moderately organized bowing
segments have been noted along this line for several hours, with
isolated wind damage reports earlier this morning. The air mass
ahead of the line is slowly destabilizing over southeast LA, with
temperature warming into the 70s and mid 60s dewpoints now in place.
Given the relatively strong wind fields, the organization of the
ongoing convective line, and the timing of the storms moving through
southeast LA at peak diurnal time, will add a small SLGT risk area
for this region. Damaging winds would be the main risk, although an
isolated tornado is also possible.

...MO/IA/IL...
Latest surface analysis shows a deep low over eastern KS. This low
will track northeastward toward southwest IA this afternoon, with a
warm front lifting northward into southern IA and western IL.
Visible imagery shows clearing/heating occurring over northern MO,
where temperatures in the 60s and dewpoints around 50F will combine
with cold mid-level temperatures to yield MLCAPE values of 400-800
J/kg. Forecast shear profiles will support low-topped supercells
capable of hail, gusty winds, and a tornado or two. 12z CAM
guidance varies on corridor of max potential, and low CAPE values
limit the confidence of a more robust severe threat. Nevertheless,
an upgrade to SLGT is possible at 20z if a more focused area of
concern develops.

..Hart/Moore.. 03/23/2021

$$
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ACUS01 KWNS 241620
SWODY1
SPC AC 241618

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1118 AM CDT Wed Mar 24 2021

Valid 241630Z - 251200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
AND TONIGHT FROM CENTRAL INTO NORTHEAST TEXAS...

...SUMMARY...
Severe thunderstorms capable of large hail, damaging winds, and
isolated tornadoes will be possible over parts of the southern
Plains into the Arklatex, mainly this evening into tonight.

...North-Central TX this afternoon...
Latest visible satellite loop shows relatively clear skies across
much of north-central and northeast TX, with temperatures warming
through the 60s. Meanwhile, a surface warm front is lifting
northward into this area, with 50s dewpoints now as far north as
ACT. This destabilizing process will continue through the
afternoon, yielding MLCAPE values over 1000 J/kg. Forecast
soundings show little cap, and CAM guidance indicates the likely
development of scattered thunderstorms across the warm sector and in
vicinity of the warm front. Supercell structures are expected with
large hail being the main threat. As the low-level moisture
continues to improve through the evening, isolated tornadoes will
also be possible as activity spreads into northeast TX.

...Central TX tonight...
Water vapor imagery shows a shortwave trough over northern Mexico
rounding the base of the larger-scale trough. This feature will
emerge into southwest TX after dark, leading to the development of
scattered thunderstorms. Similar to farther north, supercells
capable of large hail and a tornado or two appears to be the main
threat, although the potential for damaging winds could also
increase with time. This cluster of storms is expected to track east-northeastward through the pre-dawn hours into east TX, with a
continued severe risk.

...Southern AR/northwest MS...
A surface warm front is forecast to become better defined by evening
over central MS/LA and lift northward overnight. Thunderstorms are
expected to develop along and north of this boundary after midnight.
Meanwhile, model guidance is consistent in a strengthening low-level
jet late tonight across this region - yielding enlarged hodographs
and considerable low-level shear. It is unclear if the convection
along the immediate warm front will be surface-based. However, if
these storms can be rooted in the boundary-layer, the potential
exists for supercells and bowing structures capable of damaging
winds or an isolated tornado.

..Hart/Moore.. 03/24/2021

$$
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ACUS01 KWNS 251246
SWODY1
SPC AC 251245

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0745 AM CDT Thu Mar 25 2021

Valid 251300Z - 261200Z

...THERE IS A HIGH RISK OF SEVERE THUNDERSTORMS WITH A TORNADO
OUTBREAK EXPECTED ACROSS PARTS OF NORTHERN MISSISSIPPI...NORTHERN
ALABAMA...AND SOUTHERN TENNESSEE...

...SUMMARY...
A tornado outbreak -- including the threat of a few long-tracked,
violent tornadoes -- is expected today into early this evening over
the Southeast, especially parts of Mississippi, Alabama and
Tennessee. Tornadoes, large to very large hail, and damaging winds
to hurricane force also are possible over a broad area from the
central Gulf Coast to the Ohio Valley and southern Appalachians.

--- Technical Discussion ---

...Synopsis...
In mid/upper levels, a longwave trough will be maintained over the
western CONUS, as a strong shortwave trough and related speed max
dig south-southeastward across the interior Northwest, and a
formerly basal trough ejects northeastward. The latter trough is
evident in moisture-channel imagery over the southern High Plains to
the Big Bend region of TX, and will move to MO/AR by 00Z. By 12Z,
this feature should reach Lake Erie and OH. This trough will pack
the height gradient to its southeast enough to yield 110-130-kt
250-mb flow and 80-100-kt 500-mb winds over much of the Mid-South,
and Tennessee/Ohio Valleys today and this evening.

The associated surface low-pressure area was analyzed at 11Z across
western AR to northwestern LA, still poorly consolidated around
areas of rain-cooled air. A cold front was drawn from northwestern
LA across southeast TX the middle TX Coast and deep south TX. A
"synoptic" warm front arched from the low-pressure

ACUS01 KWNS 261628
SWODY1
SPC AC 261626

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1126 AM CDT Fri Mar 26 2021

Valid 261630Z - 271200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
ACROSS UPSTATE NY AND VT...

...SUMMARY...
Damaging winds will be possible this afternoon across upstate New
York and Vermont. Elsewhere, isolated strong to severe
thunderstorms may occur today across parts of the Southeast today,
and across the central Plains and lower Mississippi Valley late this
afternoon into tonight.

...Upstate NY/VT this afternoon...
A pronounced midlevel shortwave trough and associated 995 mb surface
cyclone will move quickly east-northeastward across upstate NY and
northern New England this afternoon/evening. A narrow corridor of
surface heating and cloud breaks will spread northward/northeastward
into upstate NY and parts of VT this afternoon, immediately in
advance of the zone of ascent with the shortwave trough/surface
cyclone. A band of storms with embedded bows and/or low-topped
supercells is expected to evolve this afternoon across upstate NY,
with an associated threat for damaging winds, given SBCAPE of
500-1000 J/kg, effective bulk shear in excess of 50 kt, and 50 kt
flow within a few thousand feet of the ground. Low-level shear may
also be strong enough for a brief tornado with embedded small-scale circulations.

...Southeast AL/GA/Carolinas today...
A broken band of storms is ongoing from central GA into central SC
and eastern NC, along and just ahead of a weak, slow-moving cold
front. The primary associated shortwave trough is passing well
north of this region, and forcing for ascent appears to be near or
past peak. Still, lingering moderate buoyancy and deep-layer west-southwesterly shear could support the potential for isolated
damaging gusts and marginally severe hail, prior to the storms
weakening by this evening.

...Northern KS/southeastern NE this evening...
A lead shortwave trough over the central High Plains will eject east-northeastward today into early tonight, which will help
maintain weak surface cyclogenesis across western KS through this
afternoon. Moisture return in the warm sector will remain quite
limited in the wake of a prior frontal passage, but strong surface
heating and boundary-layer dewpoints of 48-50 F could support weak surface-based buoyancy by late afternoon into central KS. Surface heating/mixing could be sufficient for thunderstorm development
along the surface warm front to the east of the triple point by this
evening, where profiles would favor low-topped supercells.
Otherwise, the more probable scenario is for elevated convection
this evening into early tonight across northeast KS and vicinity, in
the warm advection zone (north of the surface front) on the nose of
a developing low-level jet.

...Mid South late tonight...
The stalling front near the northern Gulf coast will begin to return
northward as a warm front tonight, in response to strengthening
southerly low-level flow downstream from a southern Rockies midlevel
trough. The increase in low-level flow will likewise support
strengthening warm advection, and an increasing potential for
thunderstorm development north of the warm front overnight into the
Mid South. The returning moisture and lingering midlevel lapse
rates greater than 7 C/km will contribute to MUCAPE of 1500-2000
J/kg, and the potential for a few strong updrafts. Cells/clusters
overnight will have the potential to produce isolated large hail,
especially if any elevated supercells form given effective bulk
shear of 35-40 kt.

..Thompson/Lyons.. 03/26/2021

$$
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ACUS01 KWNS 270553
SWODY1
SPC AC 270551

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1251 AM CDT Sat Mar 27 2021

Valid 271200Z - 281200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM SOUTHERN
ARKANSAS TO MIDDLE TENNESSEE...

...SUMMARY...
Severe storms are expected across the lower Mississippi through
Tennessee Valley regions. All hazards are possible including very
large hail, damaging wind, and tornadoes. Potential for a strong
tornado exists from eastern Arkansas into western Tennessee. Other
severe storms are possible across a portion of the Midwest with
isolated damaging wind and large hail the main threats.

...Lower MS Valley/TN Valley...

Large-scale heights will not change appreciably until late in the
day1 period across the lower MS and TN Valley region. Water-vapor
imagery depicts an upper low digging southeast across AZ early this
morning. This feature is forecast to translate across far West TX
during the evening before deamplifying as it ejects into
north-central TX late. Prior to the influence of this feature, one
LLJ branch will extend across the TX Coast-LA-middle TN. Low-level
warm advection in association with this feature is expected to
encourage a considerable amount of convection that should be ongoing
at the start of the period. Several members of the HREF suggest a
possible MCS may evolve over middle TN, then propagate east during
the day. Areal extent of this activity may greatly influence
convective development later in the day as rain-cooled boundary
layer may establish an outflow boundary that could drape west across
TN.

Strongest low-level heating will be noted south of this rain-cooled
air mass, and buoyancy should be greatest from northeast TX into
northern MS where SBCAPE will exceed 2000-2500 J/kg. With
temperatures warming into the mid-upper 70s, it appears surface
parcels will reach their convective temperatures by 20z and
scattered discrete storms will likely develop from the Arklatex,
northeast toward the early-day outflow boundary over western TN.
This corridor will likely experience significant convective coverage
by the end of the period.

Forecast wind profiles favor supercells and lapse rates should be
sufficiently steep for very large hail with storms across the
western half of the ENH Risk. Tornadoes are also possible, a few
potentially strong, with discrete storms, though QLCS-type spin ups
are also possible as a squall line matures later in the evening. As
the squall line matures, the threat for strong, damaging winds will
become more likely as deep-layer westerly flow increases across the
mid-South Region.

Farther north, strong mid-level height falls will overspread the
upper Midwest region in advance of a northern branch short-wave
trough that will dig into WI/IA/MO by 28/12z. It's not entirely
clear how much moisture/instability will be drawn north ahead of the
surface low into eastern MO/IL prior to convective initiation. 00z
NAM suggests mid 50s surface dew points will advance across this
region which will help destabilization; however, nearest mid 50s
surface dew points are roughly 300 mi south across southeast
AR/northern MS. If early-day convection disrupts this moisture flow,
then somewhat less buoyancy may be available for convection
extending ahead of the low into central IL. At this time wind/hail
appear to be the primary risks with robust storms along the front.

..Darrow/Dean.. 03/27/2021

$$
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ACUS01 KWNS 271957
SWODY1
SPC AC 271955

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0255 PM CDT Sat Mar 27 2021

Valid 272000Z - 281200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
INTO TONIGHT FROM PARTS OF THE ARK-LA-TEX ACROSS THE MID SOUTH AND
TN VALLEY...

...SUMMARY...
Severe storms are likely this afternoon into tonight from the
Ark-La-Tex east-northeastward across parts of the Mid South and
Tennessee Valley. All hazards are possible including very large
hail, significant damaging winds, and a couple of strong tornadoes.

Only minor changes have been made to adjust for the ongoing cluster
of storms moving east across North Carolina. Elsewhere, the forecast
remains on track. See the previous discussion for more details.

..Wendt.. 03/27/2021

.PREV DISCUSSION... /ISSUED 1124 AM CDT Sat Mar 27 2021/

...Mid South/TN Valley region through tonight...
Elevated convection with a marginal hail threat that formed
overnight in a zone of warm advection, along and north of the
surface warm front from the Mid South into middle/eastern TN,
persists as of late morning. The convection is also associated with
a subtle mid-upper speed max moving east-northeastward over the Mid
South. Farther west, additional storm development is expected by
early-mid afternoon along the rain-reinforced front close to the
MS/AL/TN border region. This afternoon convection will likely be
rooted at the surface as the low levels continue to warm/moisten
from the south, with a few supercells possible with MLCAPE near 2000
J/kg, effective bulk shear near 50 kt, and effective SRH around 150
m2/s2.

Farther west into northeast TX and southern/eastern AR,
surface-based supercell development is expected by mid afternoon
along the moisture gradient/warm front, as the low levels continue
to destabilize and the cap weakens. The forcing for ascent will be
rather subtle, so the primary storm mode should be a mix of discrete
supercells and clusters moving east-northeastward along the buoyancy gradient/front this afternoon into early tonight. Isolated very
large hail, damaging winds, and a couple of tornadoes will be the
main concerns this afternoon. Some increase in low-level shear is
expected this evening, which will support an increase in the tornado
threat, with an isolated strong tornado or two possible. Otherwise,
storms overnight should consolidate into more of a solid band as the
synoptic cold front overtakes the convection from the northwest, in
response to phasing of the northern and southern streams, with
cyclogenesis from IL to Lower MI.

...Eastern OK/northwestern AR to IL this afternoon/evening...
The primary surface cyclone is expected to begin deepening this
evening across IL, before moving to Lower MI overnight. In the wake
of the low, a cold front will begin to accelerate southeastward
later this evening into tonight. The primary uncertainties along
this corridor are the degree of low-level
moistening/destabilization, and the magnitude of the low-level
shear. The main low-level mass response/low-level jet will likely
be directed into the rather persistent zone of convection farther to
the southeast along the effective warm front from northeast TX to
western TN. These factors suggest substantial limitations to the
wind/hail threat along the cold front farther to the northwest, with
the most questionable area centered on northwestern AR.

...Carolinas this afternoon/evening...
The cluster of storms in eastern TN has been elevated through the
morning, but some northward expansion of the surface warm sector is
expected through this afternoon from SC into NC. Given sufficient
deep-layer vertical shear, an organized cluster with some threat for
damaging winds/large hail may persist into the afternoon along the
warm front from the Piedmont eastward across NC and adjacent
portions of SC.

$$
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ACUS01 KWNS 280556
SWODY1
SPC AC 280555

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1255 AM CDT Sun Mar 28 2021

Valid 281200Z - 291200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS
SOUTHEASTERN VIRGINIA AND ADJACENT FAR NORTHEAST NORTH CAROLINA...

...SUMMARY...
Scattered severe storms are likely along an advancing cold front
from the Mid-Atlantic into the Carolinas. The highest confidence in
damaging winds is in southeastern Virginia and vicinity. Farther
south and west, a few strong to severe storms are possible from
Mississippi into Georgia.

...Synopsis...
Shortwave trough currently extending from the Upper Midwest back
southwestward through the central Plains will continue eastward
throughout the day, moving through the Great Lakes, OH Valley,
Mid-Atlantic and much of the Northeast. As it does, the system is
expected to mature significantly, with both a deep surface low over
southern Quebec and strong mid-level flow from the TN Valley into
the Mid-Atlantic predicated by this afternoon.

A cold front will also accompany this system. Expectation is for
this front to extend from western NY southwestward along the central
and southern Appalachians by around 18Z this afternoon. The front is
forecast to be off the Northeast and Mid-Atlantic coasts by 00Z
Monday. A broad area of at severe potential will exist of this front
from the northern Mid-Atlantic into the Southeast.

...Mid-Atlantic/Carolinas...
Ongoing convective system over the TN and Lower MS Valleys is
expected to continue eastward/northeastward this morning and into
this afternoon. Most of the 00Z guidance is too slow with the
forward progression of the system, particularly the portion entering
middle TN, where more forward propagation has been noted. While some
slowing of convective line is likely has instability wanes with
eastern extent, overall expectation is for this area of convection
to reach central VA/NC this morning.

As such, severe potential across the region will be tied to the
potential for re-development along the front. The bulk of the
guidance suggests destabilization will occur ahead of the front, and
that a strongly forced line will develop along the front. Intense
low to mid-level flow will favorable strong, convectively enhanced
wind gusts within this line. A few embedded tornadoes are possible
as well.

Given this severe potential, 30% wind/5% probabilities will be
maintained with this outlook. However, uncertainty regarding the
stability of the air mass preceding the front merits close
observation of overnight trends and guidance, with potential
downgrades needed in subsequent outlooks.

...Southeast...
Modest buoyancy will continue to promote thunderstorm development
along the front as it moves across the region this morning and into
this afternoon. Low-level winds will likely veer before frontal
passage and stronger flow aloft will be increasingly displaced
north. However, the environment will remain conducive to
occasionally organized storms capable of strong downbursts. A brief
tornado or two could also occur within the line, particularly over
northern GA where low-level flow is expected to remain strong as the
line moves through.

..Mosier/Karstens.. 03/28/2021

$$
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ACUS01 KWNS 282000
SWODY1
SPC AC 281959

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0259 PM CDT Sun Mar 28 2021

Valid 282000Z - 291200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SOUTHEASTERN
VIRGINIA...

...SUMMARY...
Scattered severe thunderstorms capable of wind damage and a tornado
or two are expected across the Carolinas and Mid-Atlantic States
this afternoon into the evening. Isolated wind and hail will be
possible in the Southeast for the next few hours.

...Southeast Virginia into North Carolina...
Storms have developed along a pre-frontal trough and will continue
to progress eastward into eastern NC and parts of southeast VA.
Additional development is expected to occur along the cold front,
but dewpoints mixing into the low 60s/upper 50s F and early-day
cloud cover has limited surface heating and hindered surface-based
instability. The Enhanced risk area has been adjusted to where the
best overlap of buoyancy and mid-level winds still exists.

...Southeast...
Convection along the front continues to progress southeastward.
Probabilities have been adjusted where the airmass has already been
overturned. The expectation for the ongoing convection is that it
will generally weaken as it moves east into a less unstable airmass.
However, isolated wind damage and marginally severe hail will be
possible for the next few hours.

..Wendt.. 03/28/2021

.PREV DISCUSSION... /ISSUED 1125 AM CDT Sun Mar 28 2021/

...Synopsis...
A band of rain and embedded thunderstorms persists along and just
ahead of a surface cold front from AL/GA across the Piedmont of the Carolinas/VA, in advance of a midlevel shortwave trough over the
OH/TN Valley regions. The primary associated surface cyclone will
continue to move northeastward near the Saint Lawrence Valley, while
the cold front likewise progresses eastward to the Mid-Atlantic and
southeast Atlantic coasts this evening into early tonight. There
will be a window of opportunity for severe storms in the zone of destabilization preceding the cold front/rain band this afternoon
across the Carolinas into the Chesapeake Bay region.

...NC into VA this afternoon/evening...
Cloud breaks are occurring across central/eastern NC and
southeastern VA in advance of the frontal rain band and thicker
clouds. Temperatures are warming into the 70s with boundary-layer
dewpoints in the mid 60s, which is driving MLCAPE of 500-1000 J/kg
and some deepening cumulus near the SC/NC border. Deep-layer flow
and vertical shear will remain strong over the area this afternoon,
per VWPs with 50-60 kt flow within the lowest 1-3 thousand feet
above the ground. The primary uncertainty will if there can be any
substantial destabilization behind the lead cloud/rain band now
moving across NC/VA. Satellite imagery suggests that the clouds are
rather thick and will be sufficient to limit surface heating through
the afternoon to the north of southeastern VA. In that scenario,
the stronger storms would likely have to evolve from convection
along or just ahead of the pre-frontal band which will cross
southeastern VA and northeastern NC this afternoon, which is where
the confidence in damaging convective gusts (and perhaps a tornado)
is a bit higher.

...Mid-Atlantic into southern NY this afternoon/evening...
As previously mentioned, the degree of destabilization is more in
question with northward extent across VA/MD/DE toward eastern PA and
NJ. Surface temperatures in the 65-70 F range will be needed to
much in the way of SBCAPE and a damaging-wind threat with a forced
band of convection along the cold front. Will maintain the
character of the previous outlook, but the northward extent of the
severe threat will depend on some cloud breaks this afternoon. The
Marginal area has been expanding some into southern NY to reflect
the potential for just enough low-level warming/moistening to
support minimal SBCAPE and the low chance for strong/damaging gusts
with a shallow convective band along the cold front.

...SC/GA this afternoon...
The convection from overnight persists in a band just ahead of the
surface cold front. Low-level forcing for ascent will be maintained
along the convective band today, and in tandem with surface heating
and modest low-level moisture/buoyancy could support a continued
threat for at least isolated damaging gusts through the afternoon.

$$
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ACUS01 KWNS 291602
SWODY1
SPC AC 291601

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1101 AM CDT Mon Mar 29 2021

Valid 291630Z - 301200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected across the continental United
States through tonight.

...FL...
A relatively quiet convective day is forecast across the CONUS
today, with dry/stable conditions in most areas. One exception will
be over the central and southern FL peninsula. A stalled surface
boundary lies across central FL, with a moist and marginally
unstable air mass to its south. A few showers and isolated
thunderstorms are expected to form over this region this afternoon
and evening - perhaps persisting through midnight along the east
coast. No severe storms are anticipated.

..Hart/Lyons.. 03/29/2021

$$
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ACUS01 KWNS 301559
SWODY1
SPC AC 301557

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1057 AM CDT Tue Mar 30 2021

Valid 301630Z - 311200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
AND TONIGHT FROM THE ARKLATEX REGION INTO THE TENNESSEE VALLEY....

...SUMMARY...
Thunderstorms are expected to develop across the ArkLaTex region and
lower Mississippi through Tennessee Valleys, mainly late this
afternoon and tonight, with isolated strong/severe thunderstorms
possible.

...Arklatex into the Tennessee Valley...
Morning water vapor loop shows a broad upper trough across the
northern Plains and Rockies, with moderately strong
west-southwesterly flow aloft extending from TX into the southeast
states. A cold front is pushing southeastward across OK/MO and will
move into the Arklatex and TN Valleys tonight. Southerly low-level
winds ahead of the front will help to moisten/destabilize the
region, with dewpoints in the 60s and MUCAPE values of 500-1000 J/kg
this evening and tonight. This will lead to a rather broad area of
scattered thunderstorm potential. 12z CAM solutions generally agree
in isolated coverage of storms, and suggest that weak large-scale
forcing will limit the overall updraft/downdraft intensities.
However, forecast soundings show profiles generally favorable for
the risk of hail and gusty winds in the stronger cells that can
develop. Therefore, will maintain the broad MRGL risk category at
this time.

..Hart/Lyons.. 03/30/2021

$$
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ACUS01 KWNS 311629
SWODY1
SPC AC 311627

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1127 AM CDT Wed Mar 31 2021

Valid 311630Z - 011200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS CENTRAL GULF COAST
TO THE CAROLINAS...

...SUMMARY...
Scattered damaging winds, a couple brief tornadoes, and marginally
severe hail will be possible across portions of the Southeast States
through this evening.

...Central Gulf Coast to AL/GA...
A convective swath is ongoing from north GA west-southwest to
central LA with deeper embedded cores near the MS/AL border area,
along a southeast-moving cold front. Weak mid-level lapse rates
sampled by area 12Z soundings will be a limiting factor to
instability, but low-level destabilization is underway with
warm-sector cloud breaks. This will likely support an increasingly
expansive plume of modest buoyancy (MLCAPE of 500-1500 J/kg) from
the Lower MS Valley towards the AL/GA border, and contribute to an
uptick in convective intensity through this afternoon. Embedded
bowing segments will be possible as boundary-parallel shear vectors
favor a quasi-linear storm mode. Scattered damaging winds are likely
to be the most common threat, but a brief tornado is possible.

...Carolinas...
An MCV in northwest GA should track along the lee of the southern
Appalachians along composite outflow from downstream showers across
the western Carolinas. This will aid in potential for organized
clusters and a QLCS during the late afternoon to early evening.
These clusters/QLCS should develop as the MCV impinges on a
destabilizing air mass across the Piedmont, supported by
boundary-layer heating amid a plume of upper 60s surface dew points
emanating north from the South Atlantic Coastal Plain. While
mid-level lapse rates will remain weak, MLCAPE of 500-1500 J/kg
should become common. With convective activity expected to outpace
movement of the surface cold front, the region should largely lie
along the eastern periphery of stronger mid-level southwesterlies.
With 30-35 kt effective shear, scattered damaging winds should be
the primary hazard, but a brief tornado is possible.

..Grams/Lyons.. 03/31/2021

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ACUS01 KWNS 011619
SWODY1
SPC AC 011618

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1118 AM CDT Thu Apr 01 2021

Valid 011630Z - 021200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
AND EVENING OVER PORTIONS OF SOUTHEAST FLORIDA...

...SUMMARY...
Isolated strong/severe thunderstorms may impact parts of the
southeast Florida Peninsula late this afternoon through early
evening, posing at risk of hail and localized damaging wind gusts.

...Southeast FL...
Latest visible satellite imagery shows mostly clear skies over
southeast FL, where dewpoints in the upper 60s and relatively cool
temperatures aloft will yield afternoon MLCAPE values approaching
2000 J/kg. A cold front is sagging into the area, and will help to
initiate scattered thunderstorms through the afternoon. The primary
mitigating factor to a greater severe threat is the weak convergence
along the front. Local VAD profiles show west-northwesterly
low-level winds ahead of the front. This may focus the strongest
storms along the east-coast sea breeze, but should limit
thunderstorm intensity along the front. The potential exists for
hail and gusty/damaging winds in a few of the storms before they
move offshore this evening.

..Hart/Lyons.. 04/01/2021

$$
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ACUS01 KWNS 020555
SWODY1
SPC AC 020554

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1254 AM CDT Fri Apr 02 2021

Valid 021200Z - 031200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are expected today across parts of the southern
Rockies and southern High Plains. Elsewhere across the continental
United States thunderstorms are not forecast today or tonight.

...DISCUSSION...
Southwest mid-level flow will be in place today across the eastern
half of the nation. Further west, an upper-level low will move
eastward across the Desert Southwest. Large-scale ascent associated
with the low will spread eastward across the southern Rockies and
into the southern High Plains. Enough moisture and instability is
forecast ahead of the upper-level low for isolated thunderstorm
development from late this afternoon and evening into the overnight
period. Instability should be too weak for a severe threat.
Thunderstorms are not expected across the remainder of the
continental United States today or tonight.

..Broyles.. 04/02/2021

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ACUS01 KWNS 030600
SWODY1
SPC AC 030558

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1258 AM CDT Sat Apr 03 2021

Valid 031200Z - 041200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms will be possible today into tonight from parts of New
Mexico southeastward into south-central Texas.

...DISCUSSION...
An upper-level trough will move eastward from southern New Mexico
into far west Texas today. Low-level moisture advection will take
place today across southern and central Texas ahead of the
upper-level trough. As surface temperatures warm, weak instability
is forecast to develop on the northwestern edge of the moist sector.
This will result in the possibility of isolated thunderstorm
development from parts of southeast New Mexico eastward across much
of west and central Texas. As the upper-level trough moves into the
southern High Plains this evening into tonight, a chance of
thunderstorms will exist across the Texas Hill Country. Instability
is expected to be too weak across the southern Plains for a severe
threat. Elsewhere across the continental United States, thunderstorm development is not forecast.

..Broyles.. 04/03/2021

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ACUS01 KWNS 031931
SWODY1
SPC AC 031929

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0229 PM CDT Sat Apr 03 2021

Valid 032000Z - 041200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Scattered thunderstorms will be possible through tonight primarily
from parts of New Mexico to south-central Texas.

...20z Update...

The ongoing forecast remain on track, and no changes to the previous
outlook are necessary. See previous discussion below for more
details.

..Leitman.. 04/03/2021

.PREV DISCUSSION... /ISSUED 1104 AM CDT Sat Apr 03 2021/

...NM/TX...
Another rather quiet convective day is forecast across the CONUS,
with thunderstorm potential restricted to parts of NM/TX. Scattered thunderstorms have been occurring over central/east TX this morning,
but this activity is slowly waning as low-level forcing diminishes.
New convection is expected to form over southeast NM and southwest
TX this afternoon and spread eastward overnight. An isolated strong
storm is possible over the Davis mountains this evening, but the
risk appears too low/localized to warrant a MRGL risk.

$$
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ACUS01 KWNS 041255
SWODY1
SPC AC 041253

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0753 AM CDT Sun Apr 04 2021

Valid 041300Z - 051200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms are not expected today or tonight.

...Discussion...
A nearly zonal upper-level flow regime will modestly amplify through
tonight under the influence of a southeastward-digging shortwave
trough over British Columbia and the Pacific Northwest. Increasing
lee-side troughing is expected to the south of surface cyclogenesis
across the north-central High Plains, with warm frontogenesis
expected over the Upper Midwest into tonight. Overall moisture
within the warm sector will remain limited, with strong
boundary-layer heating/mixing and weak convergence influencing the
possibility of isolated thunderstorm development late this afternoon
across Nebraska southwestward into the southern High Plains, with
increasing warm/moist advection into the upper Mississippi Valley
leading to some elevated thunderstorms tonight.

If/where storms do form, a stronger storm or two with gusty winds
might be a possibility across south-central Nebraska early this
evening and/or possibly with small hail northeastward into northern
Iowa/far southern Minnesota tonight. However, the overall
likelihood/coverage of storms is questionable, and modest moisture
and the influence of residual capping should otherwise limit severe
potential.

..Guyer/Mosier.. 04/04/2021

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ACUS01 KWNS 041954
SWODY1
SPC AC 041953

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0253 PM CDT Sun Apr 04 2021

Valid 042000Z - 051200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms are not expected today or tonight.

...20z Update...

The only changes to the previous outlook were to remove general
thunderstorm area from central Texas. Thunderstorm activity from
earlier in the day has diminished and further activity is not
expected. Otherwise, a corridor of isolated, non-severe
thunderstorms will be possible from northeast NM toward the Great
Lakes the remainder of the forecast period.

..Leitman.. 04/04/2021

.PREV DISCUSSION... /ISSUED 1120 AM CDT Sun Apr 04 2021/

...TX...
Scattered thunderstorms have been occurring this morning in an area
of low-level warm advection and lift over central TX. This activity
is expected to slowly diminish through the early afternoon. Other
isolated thunderstorms are expected to develop for a few hours this
afternoon and early evening over the Davis mountains of southwest
TX. No severe storms are anticipated today.

...NM to Lower MI...
A weak surface cold front extends from MN southwestward into western
KS. Most areas along this boundary will remain dry today. However,
several model solutions suggest the potential for isolated
high-based showers and thunderstorms during the max heating period
from northeast NM into parts of NE. Another area of convection is
expected to develop after dark over parts of WI and lower MI and
low-level warm advection strengthens. Limited moisture/instability
should preclude the risk of severe storms in these areas as well.

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