ACUS03 KWNS 140744
SWODY3
SPC AC 140744

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0144 AM CST Thu Jan 14 2021

Valid 161200Z - 171200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not expected on Saturday.

...Ohio Valley and central Appalachians...

The synoptic upper low centered over the OH Valley Saturday morning
will move generally northeast, reaching the Northeast U.S. Saturday
night. A dry continental polar airmass will reside across the OH
Valley. Weak instability resulting from surface heating, cold air
aloft and mid-level forcing for ascent attending vorticity maxima
rotating through the upper low circulation will contribute to a few
mostly snow showers. However, it appears the convective layer depth
and degree of instability will remain insufficient for
thunderstorms.

..Dial.. 01/14/2021

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ACUS03 KWNS 150727
SWODY3
SPC AC 150726

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0126 AM CST Fri Jan 15 2021

Valid 171200Z - 181200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not expected across the U.S. mainland Sunday.

An upper trough will amplify and move through the eastern U.S. on
Sunday with offshore flow over the Gulf Coast as well as along the
Atlantic Seaboard. This pattern should maintain stable conditions
inland, precluding a threat for thunderstorms.

..Dial.. 01/15/2021

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ACUS03 KWNS 160809
SWODY3
SPC AC 160808

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0208 AM CST Sat Jan 16 2021

Valid 181200Z - 191200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not expected across the continental United States
on Monday or Monday night.

...DISCUSSION...
An upper-level trough is forecast to move east-southeastward across
the upper Mississippi Valley as zonal flow remains in place over the
southern tier of the nation. At the surface, high pressure will be
located across the Southeast and Gulf of Mexico. This will prevent
moisture return limiting the potential for thunderstorm development
across the continental United States Monday and Monday night.

..Broyles.. 01/16/2021

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ACUS03 KWNS 170810
SWODY3
SPC AC 170809

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0209 AM CST Sun Jan 17 2021

Valid 191200Z - 201200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Non-severe thunderstorm development will be possible across parts of
the southern Plains from Tuesday afternoon through Tuesday night.

...DISCUSSION...
An upper-level low will remain south of the southern California
Coast on Tuesday as an upper-level ridge moves slowly across the
central Rockies and southern Plains. At the surface, a moist airmass
is forecast to be in place across south-central Texas. Thunderstorm
development occur in the Texas Hill Country Tuesday afternoon and
evening along the northwestern edge of the moist airmass. However,
instability is forecast to be very weak, suggesting the convection
will remain sub-severe. Elsewhere across the continental United
States, thunderstorm development is not expected Tuesday and Tuesday
night.

..Broyles.. 01/17/2021

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ACUS03 KWNS 180814
SWODY3
SPC AC 180813

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0213 AM CST Mon Jan 18 2021

Valid 201200Z - 211200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not expected to develop across the continental
United States Wednesday or Wednesday night.

...DISCUSSION...
West-northwest mid-level flow is forecast across much of the U.S. on
Wednesday. At the surface, high pressure is forecast to be in place
from the southern Plains eastward across the Gulf Coast States. This
will prevent moisture return limiting the potential for
thunderstorms across the continental United States on Wednesday and
Wednesday night.

..Broyles.. 01/18/2021

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ACUS03 KWNS 200708
SWODY3
SPC AC 200707

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0107 AM CST Wed Jan 20 2021

Valid 221200Z - 231200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
No severe weather is expected across the U.S. Friday.

...Discussion...
Substantial amplification of the large-scale pattern is expected
Friday, as the short-wave trough digging southeastward across the
northwestern U.S. at the start of the period strengthens with time.
By the end of the period, broad/high-amplitude cyclonic flow will
prevail over the entire western U.S., with the positively tilted
trough axis extending from Montana to central California.

At the surface, high pressure will prevail east of the Rockies
through the period, while a cold front shifts across the
Southwest/southern Rockies through the period.

With dry/stable conditions prevailing east of the Rockies,
thunderstorms are not expected. In the West, cold air/steep lapse
rates aloft -- associated with the upper trough -- will support scattered/showery convection. While a lightning flash or two cannot
be ruled out, any coverage would likely be less than 10%.

..Goss.. 01/20/2021

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ACUS03 KWNS 210758
SWODY3
SPC AC 210757

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0157 AM CST Thu Jan 21 2021

Valid 231200Z - 241200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected across the U.S. on Saturday.

...Discussion...
Slow progression of the upper pattern is expected Saturday, as the
main feature of interest -- the upper trough over the West --
continues a slow southeasterly advance. As this occurs, downstream
flow across the central and into the eastern U.S. will take on
gradual anticyclonic curvature in response.

At the surface, high pressure will remain prevalent east of the
Rockies, though a cold front crossing the Desert Southwest and
southern Rockies is progged to eventually reach the central and
southern Plains.

Similar to Friday, showers will accompany the advance of the upper
system across the West, as cold air/steep lapse rates aloft spread
slowly eastward. While a few lightning flashes may again occur over
parts of the West, anticipated coverage appears insufficient to
warrant inclusion of a 10% thunder area.

..Goss.. 01/21/2021

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ACUS03 KWNS 220750
SWODY3
SPC AC 220749

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0149 AM CST Fri Jan 22 2021

Valid 241200Z - 251200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe storms are not expected across the U.S. on Sunday.

...Synopsis...
Mean long-wave upper troughing is forecast to remain over the
western U.S. this period, as smaller-scale/short-wave troughs rotate
through the broader cyclonic flow field. The first of these --
initially lying across southern California and northern Baja, is
expected to shift eastward across the Desert Southwest and southern
Rockies, and then reach the southern High Plains region as a
negatively tilted, deamplifying impulse late in the period.
Meanwhile, the second short-wave feature will lie just off the
western Canada coast initially, with an associated/elongated
north-south lobe of vorticity extending from Alaska to just off the
Pacific Northwest coast. With time, the short-wave energy will dig
southward along the West Coast, to a position just inland by the end
of the period -- thus reinforcing the pre-existing long-wave trough.

At the surface, a cold front associated with the initial short-wave
trough ejecting across the Southwest will move across New Mexico and
later Texas. East of this system, a west-to-east baroclinic zone
will become established across the Mid Mississippi and Tennessee
Valleys through the end of the period.

With much of the CONUS remaining cool and stable through the period,
deep convective potential will be limited to the southwestern and
south-central portions of the country. Cold air/steep lapse rates
aloft accompanying the upper system will support potential for
sporadic lightning flashes across portions of the Four Corners
states. Later, as downstream warm advection increases across the
south-central U.S., elevated convection -- including scattered
thunderstorms -- will likely evolve during the second half of the
period. Muted instability, however, precludes appreciable risk for
severe storms.

..Goss.. 01/22/2021

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ACUS03 KWNS 230831
SWODY3
SPC AC 230829

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0229 AM CST Sat Jan 23 2021

Valid 251200Z - 261200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe storms are not expected on Monday across the CONUS.

...Discussion...
A persistent western U.S. long-wave trough is progged to remain in
place Monday, while anticyclonic westerlies prevail over most of the
East. A short-wave trough -- ejecting from the western long wave --
is expected to deamplify with time as it shifts east-northeastward
out of the central and southern Plains, and crosses the Midwest/Ohio
Valley region into the evening and overnight. Meanwhile, a second
short-wave trough -- elongated in a north-south orientation along
the western NOAM Coast early -- is forecast to shift gradually
inland.

As this western feature slowly progresses, showers -- and areas of occasional/embedded lightning -- are expected, from the West Coast
states into the Great Basin/Four Corners states. Meanwhile, showers
and scattered thunderstorms will spread across the southeastern
quarter of the country -- as far north as the Ohio Valley and
Mason/Dixon line.

Early in the period, a few stronger storms may be ongoing across the
Arklatex region, near an Arkansas surface low and trailing cold
front. Any lingering/low-end severe risk appears at this time
insufficient to warrant any severe-weather probabilities. As the
low/front, and associated area of convection -- continues eastward
into a more stable environment, potential for robust convection
should gradually diminish with time.

..Goss.. 01/23/2021

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ACUS03 KWNS 240820
SWODY3
SPC AC 240819

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0219 AM CST Sun Jan 24 2021

Valid 261200Z - 271200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe weather is not expected across the U.S. on Tuesday.

...Discussion...
As an upper low/trough over the Gulf of Alaska digs southeastward
toward the West Coast, a trough/low over the Great Basin/Desert
Southwest will be kicked east-northeastward across the central and
southern Rockies into the Central and Southern Plains. As this
occurs, weak cyclogenesis is expected into the second half of the
period over the western Gulf of Mexico vicinity, along a remnant
baroclinic zone.

Showers, and a few thunderstorms, are expected across portions of
the central and southern Appalachians/southeastern U.S. early in the
period. Some increase in shower/thunderstorm activity may occur
during the second half of the period just a bit farther west, into
the lower Mississippi Valley area and central Gulf Coast states, as
low-level warm advection increases in response to the approach of
the next system. However, with the boundary layer expected to
remain slightly stable, and elevated instability minimal, convection
should remain generally weak/disorganized.

Elsewhere, showers -- and an occasional/embedded lightning flash --
are expected across portions of the Southwest.

..Goss.. 01/24/2021

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ACUS03 KWNS 160831
SWODY3
SPC AC 160830

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 AM CST Tue Feb 16 2021

Valid 181200Z - 191200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE FLORIDA PANHANDLE...SOUTHEASTERN ALABAMA...AND SOUTHERN/CENTRAL
GEORGIA...

...SUMMARY...
Isolated strong to severe thunderstorms may occur across parts of
the Southeast on Thursday.

...Southeast...
A large-scale, highly amplified upper trough should advance eastward
from the Plains to the MS Valley on Thursday. A belt of strong
southwesterly mid/upper-level winds will likely exist over parts of
the Southeast through much of the period. Isolated strong to severe thunderstorms may be ongoing Thursday morning near coastal AL and
the western FL Panhandle in the vicinity of a surface warm front.
Current expectations are for a weak surface low to develop
northeastward from this region into central/eastern GA by early
Thursday evening. Low-level moisture return should also occur across
much of the FL Panhandle into southern and perhaps central GA as the
warm front also lifts northward. A strong, potentially 50+ kt
low-level jet should be in place over this region. Enhanced
mid-level flow and related deep-layer shear will be more than
adequate to support organized severe convection.

The primary limiting factor appears to be instability, which may be
rather weak owing to fairly poor mid-level lapse rates and only
modest diurnal heating across the warm sector. Even so, this weak
instability will probably be enough for surface-based storms.
Convection should increase in coverage and intensity through
Thursday afternoon along an eastward-moving cold front attendant to
the surface low, with additional storms possibly developing across
the open warm sector. Greatest potential for at least isolated
severe storms appears to be over parts of the FL Panhandle,
southeastern AL, and southern/central GA, where mid to upper 60s
surface dewpoints should be present. Given the strong low-level jet
and potential for storms to congeal into a line along the cold
front, at least isolated damaging wind gusts should be a threat.
Some low-level hodograph curvature should also prove favorable for a
couple tornadoes, especially if any discrete supercells ahead of the
line can interact with the warm front. Boundary-layer instability is
forecast to become less with eastward extent into north
FL/southeastern GA and the Carolinas. But, an isolated threat for
strong to severe thunderstorms may persist Thursday evening/night
across parts of central/eastern SC and coastal NC along/south of the
surface low and warm front.

..Gleason.. 02/16/2021

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ACUS03 KWNS 170823
SWODY3
SPC AC 170822

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0222 AM CST Wed Feb 17 2021

Valid 191200Z - 201200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms may occur Friday across the Florida Peninsula
and coastal Georgia, South Carolina, and North Carolina. Organized
severe thunderstorms appear unlikely at this time.

...Florida Peninsula...
A cold front will move southeastward across much of the FL Peninsula
through the day as a highly amplified upper trough continues
advancing over the eastern CONUS. Although low-level moisture is
expected to increase ahead of the front across the FL Peninsula,
forecast soundings across this region show very poor mid-level lapse
rates, which will likely limit instability. Low-level flow should
also veer to southwesterly ahead of the front, with only weak
convergence expected. Primary large-scale ascent associated with the
upper trough is forecast to remain generally to the northwest of the
FL Peninsula through the day, and it remains uncertain how much
convective development will actually occur along the front. Still,
strong flow at mid-levels will be present, and a strong wind gust
cannot be entirely ruled out if storms form. But, given all the
previously mentioned limiting factors, the potential for isolated
strong/gusty winds across any portion of the Florida Peninsula
appears too uncertain/conditional to include low severe
probabilities at this time.

..Gleason.. 02/17/2021

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ACUS03 KWNS 180811
SWODY3
SPC AC 180810

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0210 AM CST Thu Feb 18 2021

Valid 201200Z - 211200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not expected on Saturday.

...Synopsis and Discussion...
Surface high pressure should be centered over much of the eastern
CONUS on Saturday, with rich low-level moisture remaining offshore
from the Atlantic and Gulf Coasts. A shortwave trough should move
from the West Coast to the Rockies through the period, but
instability is expected to be too meager for lightning flashes.
Accordingly, thunderstorms appear unlikely across the CONUS on
Saturday.

..Gleason.. 02/18/2021

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ACUS03 KWNS 190711
SWODY3
SPC AC 190710

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0110 AM CST Fri Feb 19 2021

Valid 211200Z - 221200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
The risk for thunderstorms appears negligible across the U.S.,
Sunday through Sunday night.

...Discussion...
Models indicate that one short wave impulse will progress inland
across the British Columbia coast and Canadian Rockies during this
period, through the crest of initially amplified large-scale ridging
near/west of the Pacific coast, with another impulse trailing close
behind across the northeastern Pacific. As this occurs, downstream
troughing, including a couple of smaller-scale perturbations, is
forecast to turn east of the central Great Plains and southern
Rockies. Models differ concerning the evolution of the shorter
wavelength features, but weak to modest cyclogenesis appears
possible in association with the lead impulse, from the south
central Great Plains into lower Michigan by 12Z Monday. A trailing
cold front appears likely to advance across and east the Mississippi
Valley, and southward across the northwestern Gulf coast.

Despite the potentially favorable large-scale ascent associated with
this developing system, destabilization, including within the
evolving warm sector, will continue to be hampered by weak moisture
return from the Gulf of Mexico, lingering melting snow and ice, and
low cloudiness associated with the return flow above the residual
cool near-surface air mass. At this time, potential for
thunderstorms appears negligible Sunday through Sunday night.

..Kerr.. 02/19/2021

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ACUS03 KWNS 200736
SWODY3
SPC AC 200735

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0135 AM CST Sat Feb 20 2021

Valid 221200Z - 231200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
The risk for severe thunderstorms appears negligible across the
U.S., Monday through Monday night.

...Discussion...
Models indicate that mid-level ridging will be maintained along an
east-west axis across the mid-latitude eastern Pacific through this
period. Within the westerlies to the north-northwest of this
feature, short wave ridging is forecast to build across the
northeastern Pacific into southwestern Alaska. As this occurs,
progressive downstream flow appears likely to take on an increasing northwesterly component near the British Columbia coast into the
Pacific Northwest, while remaining west-northwesterly to westerly
across the interior U.S. through the Atlantic Seaboard.

Within this regime, significant mid-level troughing shifting east of
the Mississippi Valley by 12Z Monday is forecast to continue
eastward. As it overspreads the Atlantic Seaboard late Monday
afternoon through Monday night, it may be accompanied by secondary
cyclogenesis off the middle and northern Atlantic coast, and a
strengthening cold front across the south Atlantic coast into the
adjacent western Atlantic.

Ahead of the front, an influx of moisture, off a moistening boundary
layer over the northeastern Gulf of Mexico, may contribute to weak
CAPE across the Florida Panhandle into parts of southern Georgia and
the Carolinas during the day Monday. However, it appears that this
instability will generally rooted above the boundary layer, and the
extent to which this may contribute to convection capable of
producing lightning remains unclear. Somewhat better potential for boundary-layer based, or near boundary-layer based, thunderstorm
development appears to exist ahead of the front across northern
portions of the Florida Peninsula and coastal North Carolina by
Monday evening. Substantially higher thunderstorm probabilities,
though, appear focused offshore Monday night, near the Gulf Stream,
in association with more favorable phasing of low-level
destabilization and forcing for ascent.

..Kerr.. 02/20/2021

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ACUS03 KWNS 210741
SWODY3
SPC AC 210740

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0140 AM CST Sun Feb 21 2021

Valid 231200Z - 241200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
The risk for thunderstorms appears negligible across the U.S.,
Tuesday through Tuesday night.

...Discussion...
The area of lowest mid-level heights over the Arctic, initially to
the north of Alaska and the Canadian Yukon and Northwest
Territories, may slowly begin to shift east-southeastward during
this period. Otherwise, models indicate that a fairly prominent,
blocking mid-level ridge will persist across the southern
mid-latitude eastern Pacific.

Within the stronger, broadly anticyclonic westerlies between these
two features, a number of short wave troughs will remain progressive
across the northeastern Pacific into British Columbia and the
Pacific Northwest. In association with the perturbations
progressing inland, it appears that flow will trend broadly cyclonic
across the Intermountain West into the Mississippi Valley, while
downstream flow trends broadly anticyclonic into the northern and
mid Atlantic Seaboard, in the wake of large-scale troughing rapidly
progressing offshore into the western Atlantic.

These developments will be accompanied by further low-level cooling
and drying across the northeastern Gulf of Mexico and the south
Atlantic Seaboard, including the Florida Peninsula. Although a
southerly return flow may develop across the western Gulf of Mexico
into the northwest Gulf coast region, it still appears that
low-level moistening will be quite modest due to slow boundary-layer
recovery in the wake of the recent Arctic intrusion.

...Northern Rockies vicinity...
Insolation beneath the western periphery of a broad pocket of cold
mid-level air (including -35 to -40C around 500 mb) may contribute
to weak boundary-layer based CAPE and scattered convective
development Tuesday afternoon, although thermodynamic profiles
probably will be mostly below freezing. It might not be out of the
question that some of this activity could become capable of
producing lightning, but it seems mostly likely that any such
occurrences will be sparse in coverage and short-lived, and
thunderstorm probabilities appear less than 10 percent.

...South Florida...
Prior to the passage of the cold front, there appears some risk for
isolated thunderstorm development near southeast coastal areas,
though probabilities exceeding 10 percent may be mostly over the
coastal waters.

..Kerr.. 02/21/2021

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ACUS03 KWNS 220731
SWODY3
SPC AC 220730

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0130 AM CST Mon Feb 22 2021

Valid 241200Z - 251200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Aside from a small portion of the Colorado Plateau into adjacent
upper Rio Grande River vicinity, the risk for thunderstorms appears
negligible across much of the U.S., Wednesday through Wednesday
night.

...Discussion...
At higher latitudes, it appears that a deep mid-level low may
continue shifting east-southeastward across the Arctic Circle
vicinity of northern Canada during this period. In lower latitudes,
models suggest that subtropical ridging centered over the Yucatan
Peninsula vicinity will remain relatively modest/flat.

Meanwhile, as a fairly vigorous short wave impulse progresses around
its northern through northeastern periphery, blocking mid-level
ridging over the subtropical eastern Pacific is forecast to build
and expand, with broad mid-level ridging also building within the
westerlies across the Aleutians through much of the northeastern
Pacific.

Downstream of the short wave impulse approaching the Pacific coast,
models indicate that the split in the westerlies inland of the
Pacific coast will become more pronounced, with short wave ridging
spreading across the Canadian Rockies into the Canadian Prairies
within a developing northern branch. Farther east, larger-scale
mid-level troughing is forecast to evolve across the Great Lakes
into the Northeast, while a vigorous short wave perturbation within
the developing southern branch continues to dig across the Great
Basin into the Southwest.

It appears that a vigorous leading short wave impulse within the
northern branch troughing will be accompanied by a modest surface
cyclone. As cold surface ridging builds beneath confluent mid-level
flow across the Great Plains into the Ohio Valley, a sharpening
surface cold front trailing the cyclone is expected to advance into
the Gulf and south Atlantic Coast states by late Wednesday night.

...Texas...
A light southerly return flow is expected to continue off a
gradually moistening boundary layer over the southwestern Gulf of
Mexico. While a relatively warm and dry lower/mid troposphere
probably may continue to generally suppress convection, NAM forecast
soundings are suggestive of an environment becoming at least close
to thunderstorm development (in association with destabilization and
lift above the southward advancing cold front) across parts of
central Texas to the east-northeast of the Hill Country by 12Z
Thursday.

...Colorado Plateau vicinity...
Strong mid-level cooling and lift associated with the digging
southern branch short wave may contribute to thermodynamic profiles
conducive to convection capable of producing lightning Wednesday
afternoon.

..Kerr.. 02/22/2021

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ACUS03 KWNS 230821
SWODY3
SPC AC 230820

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0220 AM CST Tue Feb 23 2021

Valid 251200Z - 261200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
The risk for severe thunderstorms appears negligible across the
U.S., Thursday through Thursday night.

...Discussion...
Models indicate that a large, blocking ridge, centered at mid-levels
over the southern mid-latitude eastern Pacific (between 140-160 W),
may reach peak prominence during this period. It appears likely to
remain in phase with large-scale ridging within the westerlies,
which may continue to build north of the Aleutians and through the
Gulf of Alaska. Intensifying mid-level flow on the northeastern
periphery of this feature will take on an increasing northwesterly
component near the British Columbia coast into the northern U.S.
intermountain region, with a broad area of stronger mid-level height
falls on the leading edge of this regime.

In response to these developments, models indicate that a vigorous
short wave impulse, initially near the southern Rockies, within the
southern branch of split westerlies, will accelerate
east-northeastward across the southern Great Plains and Ozark
Plateau vicinity by 12Z Friday. However, this will be preceded east
of the Rockies by the development of fairly expansive cold surface
ridging across much of the Great Plains through the Ohio and
Tennessee Valleys. And models indicate that any associated wave
development, along the front demarcating the leading edge of this
air mass across southeast Texas through the lower Mississippi
Valley, will be weak.

A continuing southerly return flow in advance of this wave may
support a weak to modest influx of moisture off the northwestern
Gulf of Mexico. In the wake of the wave, it appears that the
shallow leading edge of the cold air will nose south of the Texas
Rio Grande River vicinity, and into the western Gulf of Mexico, by
the end of the period.

...Gulf States...
Models suggest that stronger mid/upper forcing for ascent will be
focused above/well to the cool side of the initially stalling
low-level frontal zone. This is expected to overspread parts of
north central and northeast Texas late Thursday afternoon, before
developing east-northeastward into the vicinity of the southern
Appalachians by late Thursday night, with warm layers aloft capping
moisture return to the south. Associated destabilization is
forecast to remain weak, but sufficient to contribute to
thermodynamic profiles supportive of thunderstorm development. This
may coincide with a strengthening west-southwesterly jet to 40-50 kt
in the 850-700 mb layer, but with the core of this feature also
focused above a substantive surface-based stable layer, the risk for
severe weather appears negligible (particularly given the weak CAPE
evident in the forecast soundings).

...Columbia Plateau vicinity...
Large-scale ascent and strong mid-level cooling (500 mb temps to -30
to -35 C) accompanying the vigorous digging short wave may
contribute to thermodynamic profiles supportive of convection
capable of producing lightning, mainly Thursday afternoon.

..Kerr.. 02/23/2021

$$
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ACUS03 KWNS 240808
SWODY3
SPC AC 240807

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0207 AM CST Wed Feb 24 2021

Valid 261200Z - 271200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
The risk for severe thunderstorms appears negligible across the
U.S., Friday through Friday night.

...Discussion...
The southern mid-latitude eastern Pacific blocking ridge may undergo
some suppression during this period, as the first in a series of
significant short wave troughs progresses into/around its
northwestern periphery. However, ridging will remain a prominent
influence across much of the eastern Pacific. At mid-levels, models
indicate that the broad ridge axis within the westerlies may take on
a positive tilt across the northeastern Pacific, with ridging
building into the British Columbia and adjacent Pacific Northwest
coast by 12Z Saturday.

Downstream flow will take on an increasingly northerly component
across the interior West, with significant mid-level troughing
digging into the Intermountain West/Rockies vicinity. It appears
that this will force one of the more significant preceding
perturbations east-northeast of the Rockies, toward the Great Lakes
region. At least broadly cyclonic mid-level flow is expected to
prevail across much of the U.S., but models indicate that
subtropical ridging, centered near the northwest Caribbean, will
begin to build into portions of the Southeast. At the same time, a
deep mid-level vortex centered near/north of Hudson Bay may maintain
a considerable influence.

In lower levels, the leading edge of Arctic air may begin to advance
across the central Canadian/U.S. border area by late Friday night.
Otherwise, as the center of expansive preceding cold surface ridging
shifts east of the Atlantic Seaboard, a warming southwesterly to west-southwesterly return flow will develop east of the Rockies
through the Atlantic Seaboard. It appears that one remnant frontal
zone may linger across southeastern Texas into the lower Mississippi
Valley, as well as to the lee of the southern Appalachians, while
surging northward beneath a 40-70 kt southerly 850 mb jet axis,
through the Tennessee Valley and Cumberland Plateau.

...Ark-La-Tex into Cumberland Plateau...
Thunderstorm activity may be ongoing at 12Z Friday in a corridor
across the Ark-La-Tex into northern Mississippi and Alabama, aided
by moisture return and destabilization above the frontal inversion.
This likely will be supported by mid-level forcing associated with a
remnant short wave impulse emerging from the Southwest, which may
continue to contribute to thunderstorm development as it overspreads
the Tennessee Valley into the Cumberland Plateau by late Friday
afternoon. A trailing perturbation may support additional
thunderstorm activity, rooted within the elevated moist return flow,
to the west and northwest Friday night. Even if the boundary layer
to the south of the retreating front modifies more substantively
than suggested by the NAM, relatively warm layers aloft and weak
forcing for ascent are currently expected to suppress thunderstorm
development. The risk for severe hail with the elevated convection
currently appears negligible.

...Columbia Plateau...
Insolation beneath a -30 to -35 C 500 mb cold pocket may contribute
to weak boundary-layer instability and areas of convective
development across a sizable portion of the northern intermountain
region and northern Rockies. However, thermodynamic profiles
conducive to the production of lightning may be most concentrated
across parts of the Columbia Basin, where boundary-layer warming
above freezing appears most probable.

..Kerr.. 02/24/2021

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ACUS03 KWNS 250830
SWODY3
SPC AC 250830

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 AM CST Mon Jan 25 2021

Valid 271200Z - 281200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
No severe weather is expected across the U.S. on Wednesday.

...Discussion...
A fast-moving short-wave trough -- progged to be exiting the central
and southern Plains region early in the period, will continue
tracking eastward, clearing the East Coast overnight. Meanwhile,
sharp upper troughing will remain aligned roughly along the West
Coast through the period. In between, ridging aloft will exist,
with anticyclonic flow expanding to include most of the U.S. by the
end of the period, in the wake of the departing eastern system.

At the surface, high pressure will largely prevail over most of the
country. A surface front lying across the Southeast and into the
Gulf will sag southward with time, as a weak frontal wave moves off
the southeastern U.S. coast. Overnight, this front should cross the
Florida Peninsula, reaching far south Florida and the Keys by
28/12Z.

Showers and occasional thunderstorms are expected over portions of
the Southeast, in the vicinity of the aforementioned surface
boundary. Weak instability suggests disorganized -- and for the
most part elevated -- convection. Elsewhere, showers will affect
portions of the West Coast in the vicinity of the nearly stationary
upper trough, but any sporadic lightning flashes inland should
remain few and far between, insufficient for inclusion of a 10%
thunder area.

..Goss.. 01/25/2021

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ACUS03 KWNS 260749
SWODY3
SPC AC 260748

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0148 AM CST Tue Jan 26 2021

Valid 281200Z - 291200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe weather is not expected across the U.S. Thursday.

...Discussion...
The upper pattern over the U.S. will continue to feature troughs
near both the East and West Coasts, and a broad area of anticyclonic
flow covering central portions of the country. Some evolution with
respect to the eastern trough is expected, as one shorter-wavelength
feature shifts into the western Atlantic, and is replaced by a low
advancing southeastward out of Canada and into the Northeast.
Meanwhile, the more steady-state western trough will make very slow
eastward progress toward the West Coast.

At the surface, high pressure will prevail east of the Rockies, with ridging/continental air spreading southward across nearly the entire
Gulf of Mexico. In the West, a weak Pacific front will move
gradually onshore, in advance of the aforementioned upper system.

Showers are expected over the West Coast area through much of the
period, as the trough aloft slowly advances. Although an
occasional/isolated lightning flash may occur inland within the
broader area of weak/low-topped convection, coverage is currently
expected to remain too sparse to warrant inclusion of a 10% thunder
area.

..Goss.. 01/26/2021

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ACUS03 KWNS 270831
SWODY3
SPC AC 270830

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 AM CST Wed Jan 27 2021

Valid 291200Z - 301200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe weather is not expected across the U.S. on Friday.

...Discussion...
An upper low/trough over the Northeast will gradually drift
eastward/offshore, ahead of the much-more aggressive advance of the
western U.S. trough toward the central and southern Plains. This
trough, with embedded short-wave energy lying just of the southern
CA coast at the start of the period, will advance quickly eastward
across the Southwest, acquiring negative tilt with time as it
reaches the central/southern High Plains Saturday morning.

As this trough advances, surface cyclogenesis will occur, likely in
the southern Rockies vicinity. In response, southerly low-level
flow will permit above-surface theta-e advection to increase. With
remnants of the surface cP airmass lingering, surface-based
convection is not expected. However, showers over the Southwest
will expand eastward with time, with an increase in elevated
convection expected across the Texas/Oklahoma Panhandle region late.
Lightning flashes will likely be embedded within this area of
convection as it spreads eastward, though overall should remain
sporadic through the period.

..Goss.. 01/27/2021

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ACUS03 KWNS 280815
SWODY3
SPC AC 280813

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0213 AM CST Thu Jan 28 2021

Valid 301200Z - 311200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe weather is not expected across the U.S. on Saturday.

...Discussion...
A mid-level low/short-wave trough initially expected to be centered
over the central/southern High Plains region, is forecast to move
steadily east-northeastward through the period. The feature should
reach the middle Mississippi Valley vicinity during the evening, and
then continue into/across the Midwest/Ohio Valley region overnight.

At the surface, an accompanying low is forecast to move across
Oklahoma/Kansas and into Missouri by evening, and then reach the
southern Illinois/southern Indiana area by Sunday morning. A
trailing cold front will move southeastward across the southern
Plains, and later across the Lower Mississippi Valley area and into
the northwestern Gulf of Mexico.

Showers will accompany the advance of the surface system,
particularly during the second half of the period across the
Tennessee Valley region and southward across the central Gulf Coast
states. A few lightning flashes are expected nearer the pool of
colder air/steep lapse rates aloft associated with the upper system
as it shifts east-northeastward with time, within a zone from the Kansas/Oklahoma vicinity east-northeastward into Illinois.

..Goss.. 01/28/2021

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ACUS03 KWNS 290708
SWODY3
SPC AC 290707

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0107 AM CST Fri Jan 29 2021

Valid 311200Z - 011200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected on Sunday.

...Synopsis...
Guidance is in relatively good agreement that a mature/stacked
cyclone will be centered over the Mid MS/Lower OH Valleys early
Sunday. This system is then expected to move eastward as a shortwave
trough moves through it base, contributing to some re-strengthening
of the cyclone as well as secondary surface cyclogenesis over the
southern Appalachians and Carolina Piedmont. The resulting surface
low is then expected to track northeastward along the wedge front
and off NC coast by early Monday morning.

Modest low to mid-level moisture is forecast to be in place ahead of
this secondary surface low and its attendant cold front. Some
overlap will exist between this moisture and the moderate mid/upper
level flow surrounding the parent cyclone, primarily across northern
FL and southern GA. Given the strong vertical shear, some potential
for stronger storms exists in this area. However, limited heating
and poor lapse rates will temper buoyancy and the current
expectation is for only isolated thunderstorm coverage with little
severe potential.

..Mosier.. 01/29/2021

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ACUS03 KWNS 300731
SWODY3
SPC AC 300730

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0130 AM CST Sat Jan 30 2021

Valid 011200Z - 021200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not expected on Monday.

...Synopsis...
Guidance is in good agreement that the upper pattern will feature a
western CONUS ridge and an eastern CONUS trough early Monday
morning. These features are expected to move gradually eastward
throughout the day, with the upper trough ending the period
extending southward along the East Coast and the upper ridge
covering much of the central CONUS. An additional shortwave trough
will likely extend from British Columbia southwestward into the
northwest Pacific Ocean early Tuesday morning.

Dry and stable conditions are anticipated across the CONUS, with the
lack of buoyancy precluding thunderstorm development. A few deeper
convective cores are possible within the frontal band associated
with the surface low attendant to the British Columbia shortwave as
it moves ashore. However, lightning coverage should remain less than
10%.

..Mosier.. 01/30/2021

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ACUS03 KWNS 310806
SWODY3
SPC AC 310805

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0205 AM CST Sun Jan 31 2021

Valid 021200Z - 031200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not expected on Tuesday.

...Synopsis...
Upper ridging will cover a majority of the CONUS west of the MS
River early Tuesday morning, while upper troughing will extend along
the East Coast. The East Coast trough is then expected to become
increasingly negatively tilted as a shortwave trough progresses
through its base while an embedded upper low drifts over the
Northeast. The upper ridge is forecast to gradually dampen as it
moves across the Plains and into the MS Valley.

Lastly, upper trough initially extending from British Columbia into
the northeast Pacific will move eastward throughout the period. This
trough, which will feature very cold air aloft, will likely stretch
from the Canadian Prairie Provinces southwestward to a strong
embedded shortwave trough off the central/southern CA coast early
Wednesday morning.

Stable conditions are expected throughout the majority of the CONUS,
limiting thunderstorm potential. Deeper convective cores could
materialize within the frontal band moving through the Pacific
Northwest, where cold mid-level temperatures could result in a
lightning flash or two. Limited coverage and low potential for
occurrence precludes introducing any thunder areas.

..Mosier.. 01/31/2021

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ACUS03 KWNS 010726
SWODY3
SPC AC 010725

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0125 AM CST Mon Feb 01 2021

Valid 031200Z - 041200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not expected on Wednesday.

...Synopsis...
Upper pattern early Wednesday morning is expected to feature an
upper ridge over the central CONUS, flanked by two upper troughs.
Eastern upper trough will likely extend from the Northeast States to
the Bahamas while the western trough extends from the Canadian
Prairie Provinces to off the southern CA coast.

This overall pattern is forecast to move eastward, dominated by the
western CONUS troughing and its embedded shortwaves. Eastward
progression of this trough will result in surface cyclogenesis
across the High Plains, with the most dominant low emerging out of
the central High Plains and ending the period over eastern KS.

Significant cold air aloft will accompany this trough, with -30 deg
C at 500 mb reaching eastern UT/western CO by early Thursday.
Resultant steep mid-level lapse rates could result in deeper
convection as the upper trough approaches the central Rockies. A few
flashes may result, but profiles are generally expected to remain
entirely below freezing, limiting the charge separation needed for
lightning production. Stable conditions will preclude thunderstorms
elsewhere across the CONUS.

..Mosier.. 02/01/2021

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ACUS03 KWNS 020826
SWODY3
SPC AC 020825

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0225 AM CST Tue Feb 02 2021

Valid 041200Z - 051200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not expected on Thursday.

...Synopsis...
A broad and deep upper trough is forecast to cover much of the
western and central CONUS early Thursday morning, with modest upper
ridging in place east of this trough, from the TN Valley into
Quebec. A shortwave trough embedded within the larger trough is
expected to progress quickly eastward/northeastward across the
central Plains, and Mid MS/OH Valleys, reaching the Lower Great
Lakes region by early Friday morning. At the same time, another
shortwave trough is expected to move through the western periphery
of the parent trough, traversing over the Great Basin and Southwest
into the southern High Plains. Evolution of these waves will result
in broad upper troughing covering the entire CONUS by early Friday
morning.

The surface pattern early Thursday is expected to feature a large
trough from the southern Plains into western Ontario. Primary
surface low within this trough is forecast to move swiftly
northeastward throughout the day, progressing from eastern KS into
Lower MI. Cold front attendant to this low will sweep quickly eastward/southeastward, ending the period extended from Lower MI
southeastward into the Upper OH Valley and then back southwestward
into the central Gulf of Mexico.

Modest mid-level moisture will be in place ahead of this front from
the southern Plains through the Southeast. However, the stronger
forcing for ascent and the colder temperatures will remain displaced
north of the better low-level moisture. Additionally, widespread
cloud cover will limit heating. Consequently, the lack of buoyancy
will preclude thunderstorm development. Even with the expected lack
of thunderstorms, shallow convection near the surface low coupled
with strong low/mid-level flow could result convectively augmented
gusts across portions of the Lower MO and Mid MS Valleys.

..Mosier.. 02/02/2021

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ACUS03 KWNS 030737
SWODY3
SPC AC 030736

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0136 AM CST Wed Feb 03 2021

Valid 051200Z - 061200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not expected Friday.

...Synopsis...
Broad upper troughing is expected to be in place over the majority
of the CONUS early Friday. Several shortwave trough will be embedded
within this parent trough, the strongest of which will likely mature
further it moves from the Upper Great Lakes into Ontario.

A cold and stable continental air mass will dominate sensible
weather for most areas, precluding thunderstorm development. The
only exception is ahead of the cold front moving through GA and FL.
Modest low-level moisture will precede the front, but buoyancy will
be tempered by limited heating and poor lapse rates. A few flashes
are possible, particularly Friday morning across the FL Panhandle,
but coverage is expected to be less than 10%.

..Mosier.. 02/03/2021

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ACUS03 KWNS 040752
SWODY3
SPC AC 040751

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0151 AM CST Thu Feb 04 2021

Valid 061200Z - 071200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not currently expected on Saturday.

...Synopsis...
Broad upper troughing will be maintained across the CONUS throughout
the entire period, supported by several embedded shortwave troughs.
One of these shortwave troughs is forecast to extend across the central/southern High Plains early Saturday. Expectation is for this
shortwave to progress eastward throughout the day, reaching the
Lower MO Valley/Ozark Plateau by Saturday evening and the TN Valley
by early Sunday morning.

A stationary front will likely extend from central FL westward
across the central Gulf of Mexico at the beginning of the period.
Eastward progression of the aforementioned shortwave will likely
induce modest moisture return, with the stationary front
transitioning to a warm from as it gradually moves northward.
Surface cyclogenesis is also anticipated along this boundary, with
the resulting low then tracking northeastward across the central FL
Peninsula.

Some enhancement of the mid/upper level flow is also anticipated as
this wave and attendant surface low move across FL, resulting in a
kinematic environment supportive of organized storms. However,
uncertainty remains regarding the thermodynamics, particularly in
the warm sector ahead of the low where antecedent warm low to
mid-level temperatures may limit deep convection. Currently, much of
the thunderstorm activity is expected to be elevated north of the
warm front. Even so, severe probabilities may be needed in later
outlooks if the probability for warm-sector storms increases and/or
the location of the front becomes more certain.

..Mosier.. 02/04/2021

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ACUS03 KWNS 060748
SWODY3
SPC AC 060747

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0147 AM CST Sat Feb 06 2021

Valid 081200Z - 091200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe storms are not expected on Monday.

...Synopsis...

A broad upper trough will persist across much of the CONUS on
Monday. A series of shortwave impulses will pivot across the Plains,
inducing weak surface low development over OK/TX. This low will
develop eastward toward AR/LA, while a cold front dives south across
the southern Plains. As the low shifts east, a warm front will lift
northward across northern Gulf of Mexico and Florida, stalling near
the coast, from southern LA to northern FL. Widespread showers and a
few elevated thunderstorms will impact the central Gulf
Coast/Southeast vicinity in this warm advection regime late in the
period. However, weak forcing for ascent in the warm sector across
south FL, and modest buoyancy in the warm advection regime will
limit severe thunderstorm potential.

..Leitman.. 02/06/2021

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ACUS03 KWNS 070732
SWODY3
SPC AC 070731

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0131 AM CST Sun Feb 07 2021

Valid 091200Z - 101200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe storms are not expected on Tuesday.

...Synopsis...

A broad upper trough will remain over the CONUS on Tuesday. A
shortwave impulse migrating through this larger-scale trough will
dig across the southwestern U.S., resulting in weak surface lee
troughing over the southern High Plains. Meanwhile, a cold front
will move offshore the northeast and mid-Atlantic coasts, while a
stationary boundary remains draped across central TX and the
northern Gulf coast. As the upper shortwave trough pivots eastward
across the Southwest, south/southwesterly low level flow will
continue to support warm advection and isentropic ascent along the
Gulf coast. Showers and isolated thunderstorms will continue to be
possible, though forcing will remain weak and any appreciable
instability will remain offshore, precluding severe thunderstorm
potential.

..Leitman.. 02/07/2021

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ACUS03 KWNS 080737
SWODY3
SPC AC 080736

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0136 AM CST Mon Feb 08 2021

Valid 101200Z - 111200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms are not forecast on Thursday.

...Synopsis...

A low level warm advection regime will continue across parts of TX
through the Gulf coast region on Wednesday ahead of an upper trough
ejecting eastward into the Plains. In the low levels, an arctic air
mass will surge south/southeast across the southern Plains and
mid-MS/lower OH Valleys. By Thursday morning, the arctic front will
extend from the central Appalachians to northern LA, arcing
west/southwest across east TX into the Edwards Plateau.

A moist air mass will exist ahead of the front from southern/eastern
TX through the central Gulf coast. While weak instability will exist
across the warm sector, where dewpoints will be in the upper 50s to
mid 60s F dewpoints, any thunderstorm activity will likely be
elevated on the cool side of the boundary in strong isentropic
ascent. Furthermore, any storms that develop in the warm sector
would likely be quickly undercut by the south/southeastward surging
cold front given shear vectors parallel to the boundary. While a
strong storm or two can not be ruled out, overall severe potential
appears low at this time.

..Leitman.. 02/08/2021

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ACUS03 KWNS 090736
SWODY3
SPC AC 090735

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0135 AM CST Tue Feb 09 2021

Valid 111200Z - 121200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms are not forecast on Thursday.

...Synopsis...

A series of upper shortwave troughs from the central High Plains to
northwest Mexico will weaken as they shift east across the Plains
and Midwest. Strong surface high pressure will continue to develop
southward from Canada, enveloping much of the U.S. east of the
Rockies by Friday morning and bringing a very cold arctic airmass
southward. Thursday morning, a surface cold front will extend from
the TN Valley southwestward into south TX. A warm advection regime
will persist across the Gulf coast vicinity ahead of the upper
shortwave trough, with showers and isolated thunderstorms likely
ongoing across parts of the TX coastal plains into the lower MS
Valley.

Isentropic ascent with boundary-parallel deep-layer flow will result
in mainly elevated convection on the cool side of the boundary.
Surface dewpoints in the 60s F will be in place ahead of the southeastward-sagging cold front, and modest midlevel lapse rates
will aid in weak instability. While a strong storm or two can not be
ruled out, upper forcing will deteriorate as the ejecting shortwave
trough weakens. Effective shear also will remain poor in the absence
of stronger surface cyclogenesis, limiting the longevity of any
stronger elevated storms. As such, severe potential appears low at
this time.

..Leitman.. 02/09/2021

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ACUS03 KWNS 100731
SWODY3
SPC AC 100731

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0131 AM CST Wed Feb 10 2021

Valid 121200Z - 131200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms are not forecast on Friday.

...Synopsis...

Strong surface high pressure and an arctic airmass will persist
across much of the CONUS east of the Rockies on Friday. A mostly
stationary front will reside from the Piedmont of SC west/southwest
through southern AL to the mouth of the MS River and then just
offshore the TX coast. This boundary will remain nearly stationary
as another upper shortwave trough pivots southeast from CA toward
the southern Rockies during the period. This will maintain a warm
advection regime across the southeastern U.S. A narrow warm sector
will reside across FL into southern GA/AL ahead of the stationary
boundary while isentropic ascent results in showers and isolated
elevated thunderstorms from the Upper Texas Coast toward the TN
Valley. While some warm-sector thunderstorms are possible, poor
lapse rates and weak instability will preclude severe potential.

..Leitman.. 02/10/2021

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ACUS03 KWNS 120823
SWODY3
SPC AC 120822

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0222 AM CST Fri Feb 12 2021

Valid 141200Z - 151200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE FLORIDA PENINSULA...

...SUMMARY...
Isolated strong to severe thunderstorms appear possible Sunday
across parts of the Florida Peninsula.

...Florida...
Large-scale upper troughing will dominate the CONUS on Sunday. A
low-amplitude shortwave trough embedded within southwesterly
mid-level flow should advance northeastward over the Gulf Coast
states through the period. At the surface, a front near southern GA
and north FL is forecast to move little through the day. Substantial
low-level moisture is expected to remain confined along/south of
this front on Sunday.

The glancing influence of large-scale ascent associated with the
low-amplitude shortwave trough may encourage convective development
by Sunday afternoon across parts of the FL Peninsula. Forecast
soundings across this region suggest deep-layer shear will remain
strong enough to support organized updrafts. Diurnal heating of the
moist low-level airmass present along/south of the surface boundary
should foster weak to locally moderate instability by late
afternoon. The forecast combination of instability and shear appears
sufficient for isolated strong to severe thunderstorms, with
strong/gusty winds likely the main threat. This marginal severe risk
should diminish Sunday evening, as instability gradually weakens
with the loss of daytime heating.

..Gleason.. 02/12/2021

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ACUS03 KWNS 130830
SWODY3
SPC AC 130829

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0229 AM CST Sat Feb 13 2021

Valid 151200Z - 161200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHEAST...

...SUMMARY...
Isolated strong to severe thunderstorms may impact parts of the
Southeast on Monday.

...Southeast...
A highly amplified longwave upper trough should move eastward from
the Plains to the eastern states on Monday. An embedded mid-level
shortwave trough is forecast to advance northeastward from the
southern Plains across the lower MS Valley and Southeast, eventually
reaching the Mid-Atlantic by the end of the period. At the surface,
a low over the western Gulf of Mexico should develop northeastward
through the day. A warm front is forecast to advance northward along
the central Gulf Coast and into at least southern GA by Monday
night.

There is considerable uncertainty regarding how far north rich
low-level moisture will advance across the FL Panhandle and GA
Monday night ahead of the shortwave trough and deepening surface
low. The 00Z GFS and ECMWF show low to mid 60s surface dewpoints
moving farther north into GA compared to the NAM. At least weak
destabilization appears probable across the developing warm sector
late Monday evening and continuing overnight into early Tuesday
morning. The presence of a strong low-level jet and strengthening
mid-level southwesterly flow will likely foster enough deep-layer
shear to support storm organization. Given the forecast strength of
the low-level flow, both isolated strong/gusty winds and a couple
tornadoes appear possible in the vicinity of the northward-
developing warm front across the FL Panhandle and southern GA.

Too much uncertainty exists regarding the quality and northward
extent of the low-level moisture to support more than 5% severe
probabilities at this time. Additional storms should also occur
across much of the FL Peninsula during the day. Although deep-layer
shear is forecast to be weaker compared to locations farther north,
it should still be sufficient in concert with weak to potentially
moderate instability to support isolated strong to severe
thunderstorms, with occasional damaging winds the main threat.

..Gleason.. 02/13/2021

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ACUS03 KWNS 140824
SWODY3
SPC AC 140822

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0222 AM CST Sun Feb 14 2021

Valid 161200Z - 171200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms currently appear unlikely on Tuesday.

...Synopsis...
A shortwave trough should continue moving quickly northeastward from
the OH Valley and Mid-Atlantic across much of the East Coast on
Tuesday. Primary surface low over the Mid-Atlantic vicinity is
forecast to develop towards southern New England through the morning
before moving offshore. An attendant trailing cold front will move
off the majority of the East Coast early in the period, ending
thunderstorm chances for all but the FL Peninsula.

...Eastern North Carolina...
Although the cold front may not quite clear NC Coast until the first
few hours of the period, the main forcing associated with a strong
low-level jet and the mid-level shortwave trough will likely be
displaced to the north of this region. With only weak low-level
convergence along the front anticipated, any potential severe risk
appears too conditional/uncertain to include low severe
probabilities at this time.

...Florida Peninsula...
A moist low-level airmass will likely remain in place ahead of the
cold front over much of the central/southern FL Peninsula through
the day. However, this region is expected to be displaced far to the
south of any appreciable large-scale ascent aloft. Stronger
mid-level flow and related deep-layer shear are also likely to
remain north of the warm sector. Accordingly, any thunderstorms
occurring along/ahead of the front should be rather disorganized,
with generally low severe potential.

..Gleason.. 02/14/2021

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ACUS03 KWNS 150829
SWODY3
SPC AC 150828

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0228 AM CST Mon Feb 15 2021

Valid 171200Z - 181200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL GULF COAST STATES...

...SUMMARY...
Isolated severe thunderstorms may occur late Wednesday night across
portions of the central Gulf Coast.

...Central Gulf Coast...
A large-scale upper trough will continue to dominate much of the
CONUS on Wednesday. Within this feature, a shortwave trough is
forecast to move eastward from the southern Plains towards the lower
MS Valley through the period. A strong low-level mass response
should occur ahead of the shortwave trough across parts of the
Southeast, particularly Wednesday evening/night. A weak surface low
initially over the western Gulf of Mexico should develop towards the
central Gulf Coast vicinity late in the period.

There is some uncertainty regarding how far inland a warm front
extending eastward from this low will develop. Still, surface-based
storms appear possible in the last 6 hours or so of the period (late
Wednesday into early Thursday) across coastal southern LA, southern
MS/AL, and the western FL Panhandle. Forecast soundings across this
region show a strongly veering wind profile with increasing speeds
from the surface through mid levels. Effective bulk shear likely
exceeding 50 kt will support organized storms, including the
potential for isolated supercells within a strong low-level warm
advection regime ahead of the surface low. If these storms can
become surface based as low-level moisture rapidly increases late
Wednesday, then they could pose a risk for a couple tornadoes,
isolated damaging wind gusts, and perhaps even some hail as
mid-level lapse rates modestly steepen with the approach of the
shortwave trough. A Slight risk has been included to account for
where the threat for surface-based storms appears more probable. The
5% risk area encompasses a broader portion of the central Gulf Coast
states to account for uncertainty in the track of the surface low
and related low-level moisture return.

..Gleason.. 02/15/2021

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ACUS03 KWNS 100703
SWODY3
SPC AC 100702

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0102 AM CST Sun Jan 10 2021

Valid 121200Z - 131200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not expected across the contiguous U.S. on
Tuesday.

...Synopsis...
A stable pattern will persist across much of the CONUS on Tuesday as
a shortwave trough quickly exits the Mid Atlantic early in the day.
High pressure will spread across the Plains and Southeast, centered
over the Four Corners, and this will shunt any appreciable low-level
moisture offshore. To the west, strong southwest flow aloft will
persist through the period over the Pacific Northwest as a strong
jet max approaches Vancouver Island into Tuesday morning. Given that
the midlevel temperature gradient will be north of the Canadian
border, little if any CAPE is expected over WA or OR.

..Jewell.. 01/10/2021

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ACUS03 KWNS 110650
SWODY3
SPC AC 110649

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
1249 AM CST Mon Jan 11 2021

Valid 131200Z - 141200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not expected over the contiguous U.S. on
Wednesday.

...Synopsis...
A shortwave trough will move east across the southeastern states on
Wednesday, with a dry and stable air mass at the surface. The stable
air mass will also exist across the Plains, ahead of a potent
northern Rockies trough with a surface low deepening over SK and MB.
Therefore, despite this deepening upper trough Wednesday night,
thunderstorms are not expected due to lack of CAPE.

Elsewhere, an upper ridge will exist along the West Coast, with
stable conditions there as well.

..Jewell.. 01/11/2021

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ACUS03 KWNS 130725
SWODY3
SPC AC 130724

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0124 AM CST Wed Jan 13 2021

Valid 151200Z - 161200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not expected across the U.S. mainland Friday.

...Discussion...

A closed synoptic upper low will be centered across the Midwest
early Friday. This feature will move slowly east through the OH and
TN Valleys during the day. The accompanying occluded surface low
will weaken across the Great Lakes, while secondary cyclogenesis is
forecast near the Mid Atlantic coast late in the period. A front
will initially extend from the occluded low over the Great Lakes,
southeast through the southern Appalachians into the Gulf Coast
States. The front will continue east and off the Atlantic seaboard
by late Friday night. Bands of precipitation will likely occur in
vicinity of this boundary. However, very limited moisture return and
meager to no instability should preclude thunderstorm development.

..Dial.. 01/13/2021

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ACUS03 KWNS 250826
SWODY3
SPC AC 250825

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0225 AM CST Thu Feb 25 2021

Valid 271200Z - 281200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
The risk of severe thunderstorms currently appears negligible across
the U.S. for Saturday through Saturday night.

...Discussion...
Suppression of an initially prominent blocking high and amplified
mid-level ridging across the eastern Pacific appears likely to
continue during this period, as a significant short wave trough
progresses around its northern periphery, across the northeastern
Pacific. A more pronounced split in the downstream flow may develop
inland of the Pacific coast, as short wave ridging shifts across
British Columbia and adjacent portions of the U.S. Pacific
Northwest. By late Saturday night, the leading edge of this regime
may begin to translate to the north of a vigorous short wave impulse
sharply digging across the Great Basin into the lower Colorado River
vicinity of the Southwest.

Across and east-northeast of the Rockies, mid-level flow is forecast
to trend increasingly confluent, between more prominent subtropical
ridging across the Gulf of Mexico into the Southeast and a vigorous
short wave impulse pivoting southeastward out of the Arctic. As
this perturbation digs across Saskatchewan and Manitoba, an
increasingly sheared short wave impulse is forecast to accelerate
northeast of the Wyoming/Colorado Rockies toward the Upper Midwest,
while a more amplified downstream impulse accelerates east of the
Great Lakes into the Canadian Maritimes. Each of these latter
features may be accompanied by developing surface cyclones, while
cold surface ridging builds beneath the confluent flow across the
Great Plains, as far south as the Texas/Oklahoma Panhandle region by
12Z Sunday.

The net result of these developments in lower levels is expected to
be the evolution and/or reinforcement of a frontal zone near the
northern periphery of the mid-level subtropical ridging, from near
or south of the Texas Big Bend into the Mid Atlantic Coast vicinity. South/southwesterly low-level return flow, off a still modifying
boundary layer over the Gulf of Mexico, will contribute to
moistening and destabilization along and north of this front. This
will become the focus for areas of scattered thunderstorm
development Saturday through Saturday night, with models indicating
that warm layers aloft and subsidence will suppress convective
development to the south of the front.

Models do indicate that southwesterly flow around the 850 mb level
may strengthen to 40-50+ kt across the Arkansas/Kentucky/Tennessee
vicinity late Saturday afternoon and evening. It might not be out
of the question that this could contribute to a risk for organizing
storms with the potential to producing damaging surface gusts.
However, much may depend on how close convection forms to the
surface frontal position (and the depth of the near-surface stable
layer below the convection). With this uncertain, and model output
still indicating only generally weak destabilization, severe
probabilities appear less than 5 percent at the present time.

..Kerr.. 02/25/2021

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ACUS03 KWNS 260803
SWODY3
SPC AC 260802

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0202 AM CST Fri Feb 26 2021

Valid 281200Z - 011200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not currently forecast for Sunday.

...Synopsis...

A series of upper shortwave troughs will migrate across portions of
the U.S. on Sunday, bringing a large swath of strong southwesterly
flow stretching from the southern Plains through the Great
Lakes/Ohio Valley. The first shortwave trough will pivot eastward
from the Great Lakes through New England. The second shortwave
trough will become increasingly cut-off from northern stream flow as
a closed low develops over the lower CO Valley, and pivots eastward
toward the AZ/NM border by Monday morning. Downstream from the
western upper shortwave trough, weak height rises and warming
temperatures between 850-700 mb are forecast. At the surface, a cold
front will stretch from the lower OH Valley to central TX early in
the period. Surface high pressure will build over the central
Plains, and the cold front will slowly shift southward, extending
from coastal NC toward northern LA and arching southwest into
south-central TX by Monday morning.

...South-Central TX into LA/MS...

Severe potential near the aforementioned cold front is uncertain and
fairly conditional at this time. While 60s F dewpoints will exist
across the warm sector, surface heating will be limited near the
front due to widespread cloudiness. Additionally, isolated elevated thunderstorms and showers are likely to be ongoing. Weak
instability, largely driven by moderately steep midlevel lapse rates
is forecast. However, most guidance shows at least a weak capping
inversion near 700 mb. Furthermore, while effective shear will be
moderate to strong, deep-layer flow will be parallel to the front,
and low-level convergence weak. Additionally, large-scale forcing
will by weak as the upper trough remains well to the west. While a strong/marginally severe storm can not be completely ruled out, the
overall threat appears too uncertain/conditional to include probs at
this time.

..Leitman.. 02/26/2021

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ACUS03 KWNS 270811
SWODY3
SPC AC 270810

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0210 AM CST Sat Feb 27 2021

Valid 011200Z - 021200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not forecast on Monday.

...Synopsis...

An upper low over the southern Rockies will pivot eastward to the
southern Plains on Monday. Moderate to strong west-southwesterly
deep-layer flow will persist over the Plains toward the lower MS
Valley during this time. At the surface, high pressure will spread
eastward from the Plains to the Midwest and lower Great Lakes
vicinity. Meanwhile, a cold front will extend from the Delmarva
southwestward to northern LA and south-central TX Monday morning.
The cold front will continue to move southeastward through the
period, moving offshore the TX coast and stalling near the central
Gulf coast and northern FL by Tuesday morning. Widespread cloudiness
and ongoing showers and thunderstorms will limit destabilization.
Furthermore, poor midlevel lapse rates and a capping inversion
around 700 mb will preclude severe-thunderstorm potential.

..Leitman.. 02/27/2021

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ACUS03 KWNS 280738
SWODY3
SPC AC 280737

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0137 AM CST Sun Feb 28 2021

Valid 021200Z - 031200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not forecast on Tuesday.

...Synopsis...

An upper low and associated shortwave trough over the southern
Plains will migrate toward the southern/central Appalachians by
Wednesday morning. This will maintain moderate south/southwesterly
deep-layer flow and warm advection over portions of the Gulf Coast
states for much of the period. A weak surface low is forecast over
southwest Louisiana at the beginning of the period, with a cold
front extending southward from the low over the western Gulf. The
low will develop east/northeast along the central Gulf coast during
the day, and toward the South Carolina coast by the end of the
period. This will allow a warm front to lift northward along the
central Gulf coast into southern AL/GA and northern FL. While this
will create a narrow warm sector, destabilization is expected to
remain weak due to poor midlevel lapse rates and limited surface
heating. Isolated thunderstorms are expected near and to the north
of the warm front, but forecast soundings indicate this activity
will remain elevated. Overall, severe potential appears low on
Tuesday.

..Leitman.. 02/28/2021

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ACUS03 KWNS 010738
SWODY3
SPC AC 010737

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0137 AM CST Mon Mar 01 2021

Valid 031200Z - 041200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected on Wednesday.

...Synopsis...

An upper low/shortwave trough over the southern Appalachians will
move offshore by 00z as an upper ridge builds over the Rockies and
High Plains vicinity. At the surface, a cold front will extend from
a low near coastal SC southwestward into the eastern FL Panhandle
Wednesday morning. The front will track southeast across the FL
Peninsula through the period, and isolated thunderstorms are
possible near the front. Decreasing shear and a lack of stronger
forcing, coupled with weak instability, will preclude organized
severe thunderstorm potential.

..Leitman.. 03/01/2021

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ACUS03 KWNS 020757
SWODY3
SPC AC 020756

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0156 AM CST Tue Mar 02 2021

Valid 041200Z - 051200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected on Thursday.

...Synopsis...

An upper low/shortwave trough over the Four Corners vicinity will
develop eastward to the southern Plains on Thursday. In response, a
weak lee surface low will develop over the southern High Plains.
Southerly return flow will be weak, transporting mainly 40s F
surface dewpoints northward across central/eastern TX. Nevertheless,
weak elevated instability will develop as midlevel lapse rates
steepen during the evening/overnight period. As a result, isolated
elevated thunderstorms are possible across parts of the southern
Plains, mainly after 00z. This activity is not expected to be
severe.

..Leitman.. 03/02/2021

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ACUS03 KWNS 020757
SWODY3
SPC AC 020756

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0156 AM CST Tue Mar 02 2021

Valid 041200Z - 051200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected on Thursday.

...Synopsis...

An upper low/shortwave trough over the Four Corners vicinity will
develop eastward to the southern Plains on Thursday. In response, a
weak lee surface low will develop over the southern High Plains.
Southerly return flow will be weak, transporting mainly 40s F
surface dewpoints northward across central/eastern TX. Nevertheless,
weak elevated instability will develop as midlevel lapse rates
steepen during the evening/overnight period. As a result, isolated
elevated thunderstorms are possible across parts of the southern
Plains, mainly after 00z. This activity is not expected to be
severe.

..Leitman.. 03/02/2021

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ACUS03 KWNS 030752
SWODY3
SPC AC 030751

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0151 AM CST Wed Mar 03 2021

Valid 051200Z - 061200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected on Friday.

...Synopsis...

An upper low over the southern Plains will develop eastward as an
open wave across the southeastern states. At the surface, a weak low
near the OK/north TX border will weaken as it develops southeast.
Gulf return flow will remain limited to the TX coastal Plain and
portions of the Sabine Valley. However, low level moisture will
remain shallow, with low 60s dewpoints hugging the coast while upper
40s to 50s dewpoints extend further north. Steepening midlevel lapse
rates will help contribute to less than 500 J/kg MLCAPE. Stronger
forcing will remain displaced to the north/northeast of low-level
moist axis, but moderate shear and weak elevated instability should
allow for isolated thunderstorms ahead of a surface cold front.
Severe storms are not expected.

..Leitman.. 03/03/2021

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ACUS03 KWNS 040725
SWODY3
SPC AC 040724

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0124 AM CST Thu Mar 04 2021

Valid 061200Z - 071200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not expected on Saturday.

...Synopsis...

Dry and stable conditions will exist across much of the CONUS east
of the Rockies on Saturday. Strong surface high pressure and
continental trajectories will bring fair weather. The exception may
be across parts of the FL Peninsula. A cold front will quickly
progress southward through the afternoon. A few thunderstorms could
develop along the front as midlevel lapse rates steepen, in response
to cooling aloft with an upper trough pivoting offshore the Atlantic
coast. Instability will remain weak and low level shear modest,
precluding a risk for severe thunderstorms.

..Leitman.. 03/04/2021

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ACUS03 KWNS 050715
SWODY3
SPC AC 050714

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0114 AM CST Fri Mar 05 2021

Valid 071200Z - 081200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorm development may occur along the Pacific Northwest Coast
on Sunday but no severe thunderstorms are expected across the
continental United States Sunday and Sunday night.

...DISCUSSION...
Southwest mid-level flow will be in place across the northwestern
U.S. on Sunday as an upper-level low spins over the northeastern
Pacific. Large-scale ascent and mid-level moisture associated with
the upper-level system will overspread the Pacific Northwest on
Sunday. In response, thunderstorm development will be possible along
the coasts of Oregon and Washington. Instability is forecast to be
very weak and severe thunderstorm development is not expected.
Elsewhere across the continental United States, thunderstorm
development is not forecast Sunday and Sunday night.

..Broyles.. 03/05/2021

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ACUS03 KWNS 060800
SWODY3
SPC AC 060800

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0200 AM CST Sat Mar 06 2021

Valid 081200Z - 091200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorm development will be possible along parts of the West
Coast Monday and Monday night, but no severe thunderstorms are
expected.

...DISCUSSION...
An upper-level ridge will move across the mid to upper Mississippi
Valley on Monday as an upper-level low spins in the northeast
Pacific. West-southwesterly mid-level flow will be in place along
the West Coast. Strong large-scale ascent and steep mid-level lapse
rates, associated with the northeastern Pacific weather system, will
make thunderstorm development possible from the coast of Washington
southward to the coast of central and northern California. Weak
instability along this corridor will limit any potential for severe
weather. Elsewhere across the continental United States thunderstorm development is not expected Monday and Monday night.

..Broyles.. 03/06/2021

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ACUS03 KWNS 070819
SWODY3
SPC AC 070818

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0218 AM CST Sun Mar 07 2021

Valid 091200Z - 101200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorm development will be possible across parts of the West
Coast Tuesday and Tuesday night, and in parts of the north-central
states Tuesday night.

...DISCUSSION...
Southwest mid-level flow will become established across much of the
western and central U.S. on Tuesday as an upper-level moves
southward across the far eastern Pacific. Large-scale ascent
associated with the eastern edge of the eastern Pacific weather
system will overspread the coastal areas of the western U.S. This
combined with steep lapse rates will make isolated lightning strikes
possible along the coasts of Washington, Oregon and California
Tuesday and Tuesday night. Isolated thunderstorms will also be
possible further inland across central California Tuesday afternoon.

Further east into the central U.S., southwest mid-level flow will
become established during the day on Tuesday. In response, low-level
flow will increase across the Great Plains resulting in moisture
advection in the southern and central Plains. A pronounced 50 to 65
kt low-level jet is forecast to develop Tuesday night from the
southern Plains north-northeastward into the lower Missouri Valley.
This warm-advection regime may support isolated thunderstorm
development Tuesday night, along a trough of low pressure extending northeastward from the central Plains into the Upper Midwest. At
this time, thermodynamic profiles on forecast soundings near the
trough do not appear to have enough instability for a severe threat.
Any storms that form should be elevated in nature.

..Broyles.. 03/07/2021

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ACUS03 KWNS 080832
SWODY3
SPC AC 080831

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0231 AM CST Mon Mar 08 2021

Valid 101200Z - 111200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
FAR NORTHERN OKLAHOMA...KANSAS AND WESTERN MISSOURI...

...SUMMARY...
A marginal threat of severe thunderstorms with hail and strong wind
gusts will be possible from parts of far northern Oklahoma into
western Missouri, from late Wednesday afternoon through Wednesday
night.

...Far Northern Oklahoma/Kansas/Western Missouri...
Southwest mid-level flow will be in place on Wednesday across much
of the central U.S. At the surface, a low is forecast to move
northeastward across the mid Missouri Valley as a cold front
advances southeastward into southeast Nebraska and northern Kansas.
A belt of strong low-level flow will maintain moisture advection
ahead of the front during the day. Surface dewpoints are expected to
gradually increase near the moist axis, reaching the mid to upper
50s F from Oklahoma north-northeastward into northwest Missouri and
southeast Iowa. Instability will increase along this corridor during
the afternoon with model forecasts suggesting that MLCAPE values
could reach the 500 to 1000 J/kg range. Forecast soundings along the
corridor of instability from Wichita north-northeastward to Kansas
City show a capping inversion this afternoon but gradually weaken
the cap during the evening. This combined with a strengthening
low-level jet will result thunderstorm development with a gradual
increase in convective coverage in the late afternoon and evening.

As the low-level jet strengthens during the evening, continued
moisture advection should allow MUCAPE values to increase in the
1000 to 1500 J/kg range. This, combined with effective shear near 50
kt, along with 700-500 mb lapse rates approaching 8.0 C/km, should
support a hail threat. A wind-damage threat may also develop across
parts of northern Oklahoma and southeast Kansas where thunderstorms
could become more closely surface-based during the late evening and
overnight period.

..Broyles.. 03/08/2021

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ACUS03 KWNS 090833
SWODY3
SPC AC 090832

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0232 AM CST Tue Mar 09 2021

Valid 111200Z - 121200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN PLAINS AND OZARKS...

...SUMMARY...
A marginal severe threat may develop across parts of the southern
Plains and Ozarks from late Thursday afternoon into the overnight
period.

...Southern Plains/Ozarks...
Southwest mid-level flow will be maintained on Thursday across much
of the southern, central and northeastern U.S. At the surface, a
cold front is forecast to move slowly southward across northern
Oklahoma and southern Missouri. A dryline should be in place by late
afternoon from northwest Texas into western Oklahoma, where a triple
point is forecast. As surface temperatures warm during the day, a
corridor of instability should develop from northwest Texas into
central Oklahoma. Isolated convective initiation will be possible
along the northern edge of the instability. Thunderstorm development
is also expected to occur further east-northeast into parts of
northern Arkansas and southern Missouri. Thunderstorm development is
likely to continue along parts of the front during the late evening
and overnight period.

The severe threat for Thursday is highly conditional. The first
uncertainty is moisture. Low-level moisture is forecast to gradually
increase from late afternoon into the evening across the southern
Plains. Some models suggest that a small pocket of moderate
instability will develop in northwest Texas and southwest Oklahoma
by evening, where MUCAPE could approach 1500 J/kg. This combined
with effective shear in the 60 to 70 kt range and steep mid-level
lapse rates, would make a hail threat possible. Further to the
east-northeast into central and northeastern Oklahoma, surface
dewpoints are forecast to reach the lower 60s F. However,
instability in this part of Oklahoma is forecast to be less than in
areas further southwest. This combined with subsidence, associated
with a low-amplitude upper-level ridge, may marginalize any severe
threat. If a marginal severe threat does develop, it could extend as
far east as southern Missouri where the models are in agreement that
convection will develop in the late evening and overnight period.

..Broyles.. 03/09/2021

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ACUS03 KWNS 100819
SWODY3
SPC AC 100818

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0218 AM CST Wed Mar 10 2021

Valid 121200Z - 131200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
SOUTHERN PLAINS...

...SUMMARY...
A severe threat may develop Friday and Friday night across parts of
west Texas and Oklahoma. Large hail and wind damage will be
possible.

...Southern and Central Plains/Western Ozarks...
An upper-level low will move eastward across the Desert Southwest on
Friday as a shortwave ridge moves eastward into the mid Missouri
Valley and western Ozarks. At the surface, a quasi-stationary front
is forecast to be located from the southeast Texas Panhandle to
central Oklahoma and to northern Arkansas. South of the boundary
surface dewpoints are forecast to be in the upper 50s F in
northwest Texas and lower to mid 60s F across Oklahoma and Arkansas. Instability along the northern edge of the moist sector should
remain weak most of the day. Thunderstorm development will be
possible north of the front in northern Oklahoma, southern Kansas
and southwest Missouri. By late afternoon, a corridor of instability
is forecast from west Texas north-northeastward into southwest
Oklahoma, where isolated thunderstorms could develop in the northern
part of this corridor. During the evening, large-scale ascent will
increase across the southern High Plains raising the convective
potential over time.

There is considerable uncertainty concerning the forecast on Friday,
with significant spread among model solutions. An ensemble approach
would place a pocket of moderate instability over northwest Texas by
early evening with MUCAPE reaching the 1500 to 2000 J/kg range. This
combined with 60 to 70 kt of effective shear and 700-500 mb lapse
rates of 7.5 to 8.0 C/km would be favorable for supercells with
large hail. The current thinking is that a cluster of storms with
embedded supercells will develop across northwest Texas in the early
evening and spread northeastward into western Oklahoma during the
mid to late evening. In addition to hail, a wind damage threat is
expected to develop. A slight risk area has been maintained in this
corridor. A conditional severe threat may develop further to the
west across the southern Texas Panhandle, but surface dewpoints will
be considerably lower.

Further to the east in northeast Oklahoma and southeast Kansas, a
marginal severe threat may develop Friday evening. The low-level jet
will support this elevated convection, which is forecast to shift
northward with time during the overnight period. Hail will be the
primary threat with this activity but a strong wind gusts or two can
not be ruled out.

..Broyles.. 03/10/2021

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ACUS03 KWNS 110828
SWODY3
SPC AC 110828

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0228 AM CST Thu Mar 11 2021

Valid 131200Z - 141200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN PLAINS...

...SUMMARY...
A severe threat is expected to develop across parts of the southern
Plains, where large hail and wind damage will be possible. A
marginal severe threat may also develop in parts of the central
Plains.

...Southern and Central Plains...
An upper-level low will move northeastward into the central High
Plains on Saturday as a 90 to 110 kt mid-level jet moves across the
southern High Plains. At the surface, a dryline will develop and
move eastward into western Oklahoma and west-central Texas Saturday
afternoon. To the east of the dryline, a relatively moist airmass
will be in place with surface dewpoints in the upper 50s to near 60
F. Thunderstorms are forecast to develop ahead of the dryline during
the afternoon from the eastern Texas Panhandle southward into
west-central Texas. The storms are expected to move eastward across
western Oklahoma and northwest Texas during the late afternoon and
early evening.

Elevated thunderstorms are forecast to be ongoing at the start of
the period from parts of the Texas Panhandle eastward across
northern Oklahoma and southern Kansas. To the south of this
activity, a corridor of instability will develop during the late
morning and afternoon. Model consensus suggests that MLCAPE values
could reach peak near 1000 J/kg along an axis from San Angelo
northward to near Childress. This combined with 0-6 km shear near 50
kt and steep mid-level lapse rates will be favorable for supercells
with large hail. As the eastern edge of the mid-level jet moves into west-central Texas during the late afternoon, deep-layer shear is
forecast to increase to around 65 kt. This will make conditions
increasingly favorable for severe storms during the early to mid
evening. A squall-line with wind damage potential may develop during
the early to mid evening. However, any severe threat that develops
could remain somewhat isolated due to the weak instability.

Further north into Kansas, the exit region of the mid-level jet is
forecast to overspread the region during the afternoon. This will
create strong lift and deep-layer shear, favorable for an isolated
severe threat. Although organized storms can not be ruled out,
instability is expected to be very weak due to outflows from the
morning convection. Areas that are not affected by the morning
convection may have potential for marginally severe wind gusts and
hail.

..Broyles.. 03/11/2021

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ACUS03 KWNS 130800
SWODY3
SPC AC 130759

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0159 AM CST Sat Mar 13 2021

Valid 151200Z - 161200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Appreciable severe risk is not evident at this time across the U.S.
on Monday.

...Discussion...
An upper low initially over the central Plains is forecast to lift northeastward with time, becoming increasingly weak/sheared through
the period. Farther west, a second low entering northern
California/western Oregon early, is expected to pivot southeastward
across the Great Basin toward the Desert Southwest with time.

At the surface, a weak west-to-east baroclinic zone is forecast to
evolve with time, from Oklahoma eastward into the Mid South.

A band of generally weak convection should be crossing western
portions of Tennessee and Kentucky/Mississippi/eastern Louisiana and
vicinity early in the day, with some embedded/occasional lightning.
Though weak instability should limit convective intensity across
most areas, through most of the period, a small window of
opportunity for slightly more robust convection may evolve during
the afternoon, in the west-central Alabama vicinity. With shear
expected to be plenty sufficient for organized/rotating storms,
ample instability would yield potential for severe weather.
However, at this time, it appears that even through the afternoon,
CAPE should remain minimal at best. Therefore, though a stronger
storm capable of gusty winds or even a brief tornado cannot be ruled
out within a zone centered over the west-central Alabama area,
potential appears too low to highlight with a risk area at this
time.

..Goss.. 03/13/2021

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ACUS03 KWNS 140810
SWODY3
SPC AC 140809

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0309 AM CDT Sun Mar 14 2021

Valid 161200Z - 171200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE OKLAHOMA/SOUTHEASTERN KANSAS VICINITY EASTWARD INTO
MISSOURI/ARKANSAS...

...SUMMARY...
Severe weather will likely evolve during mainly during the evening
across the western Oklahoma vicinity, and then spreading across part
of Kansas, Oklahoma, and north Texas, and into Missouri/Arkansas and
vicinity. Large hail will likely be the main risk, though locally
damaging wind gusts, and possibly a tornado, will also be possible.

...Synopsis...
A fast-moving/compact upper low will move quickly across the Four
Corners to the southern Rockies by evening, and then will continue
eastward toward Oklahoma overnight. This low will be the primary
feature of interest over the U.S. through the period.

At the surface, an initially diffuse low over the northeastern New
Mexico vicinity will consolidate/deepen with time, moving across the
Texas and Oklahoma Panhandle during the evening, and into western
Oklahoma overnight. Ahead of the low, a dryline will mix eastward
across the southern High Plains during the afternoon and early even,
eventually to be overtaken by a Pacific cold front which should move
eastward across the southern Plains through the end of the period.

...Western Oklahoma vicinity to Missouri/Arkansas/the Arklatex...
Low-level moisture will stream northward across the southern Plains
beneath a capping inversion through the day, as southerly flow
strengthens with time in response to deepening low pressure shifting
into the southern High Plains. While the cap will likely hinder
convective development with southward extent across Texas, a
conditional late afternoon/early evening initiation of storms may
occur near the dryline over western Oklahoma/western North Texas.
With favorably strong/veering flow with height but modest low-level
moisture -- due to this area likely remaining on the northwestern
fringe of the moisture return -- large hail, and locally gusty
winds, would likely be the primary risks with initial
severe/supercell storm development into the early evening hours.

After dark, as the upper system continues to advance and the surface
low deepens, a strengthening low-level jet -- and associated warm
advection/QG ascent -- will likely yield a substantial blossoming of
convective development, much of which will remain elevated and
particularly so north of an anticipated Kansas/Oklahoma border-area
warm frontal zone. As such, large hail will likely remain the
primary severe potential overnight, as storms increase in coverage
through the period. Farther to the south into Texas, low-level
capping will remain a concern. However, within a zone south of the
warm front and north of the more capped airmass -- i.e. ahead of the
surface low across Oklahoma and possibly north Texas, and later
perhaps extending as far eastward into southwestern Missouri/western
Arkansas -- only a shallow stable layer is expected due to a
diurnally cooled boundary layer. Here, along with hail potential, a
couple of stronger, near-surface-based storms could also pose some
risk for locally damaging winds, or even a tornado or two, through
the remainder of the period.

..Goss.. 03/14/2021

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ACUS03 KWNS 150733
SWODY3
SPC AC 150732

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0232 AM CDT Mon Mar 15 2021

Valid 171200Z - 181200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM THE
EASTERN HALF OF ARKANSAS AND SMALL PORTIONS OF ADJACENT STATES TO
THE ALABAMA VICINITY...

...SUMMARY...
A broad area of severe weather potential -- including risk for large
hail, damaging winds, and several tornadoes -- is anticipated
Wednesday from the Arkansas/Louisiana vicinity eastward across the
central Gulf Coast states/southern Appalachians.

...Synopsis...
A vigorous upper low moving across central portions of the U.S. will
once again be the primary upper feature of interest, as it tracks
from the Texas/Oklahoma Panhandle vicinity early, to southern
Missouri through the end of the period. Ahead of this system,
moderately strong/accompanying flow will spread across the lower
Mississippi and Tennessee Valleys and central Gulf Coast states with
time.

At the surface, a low is forecast to cross Oklahoma during the day,
and then should cross the Ozarks through the evening eventually
reaching the western Illinois vicinity by 18/12Z. Widespread
thunderstorms, and substantial/accompanying severe risk, can be
expected in advance of this system.

...The AR/LA vicinity eastward to portions of TN/GA and the FL
Panhandle...
Showers and thunderstorms are forecast to be ongoing from Kansas
southward to Texas ahead of the advancing upper system and
associated cold front, and eastward across the central Gulf Coast
states in a zone along a west-to-east warm front. Some ongoing
severe risk will likely exist at the start of the period.

With time, as moisture streams northward from the Gulf of Mexico
beneath steepening lapse rates, modest heating will push
surface-based CAPE into the 1000 to 2000 J/kg range with a broad
warm sector stretching from the AR/LA vicinity eastward to the
southern Appalachians. Convection is forecast to increase in
response to the destabilization, as persistent UVV occurs not only
in the vicinity of the cold and warm fronts, but also more broadly
within the general warm-advection regime.

Southerly low-level flow, veering and increasing to around 50 kt
from the west/southwest at mid levels will provide shear favorable
for supercells. Additionally, ample low-level shear is expected to
evolve through the day -- particularly near the aforementioned warm
front which should drift northward across Arkansas and align
west-northwest to east-southeast from far southern MO to central GA
by early evening. As such, tornado risk may be maximized near this
boundary -- across the AR area during the day, and then later
increasing eastward across AL and perhaps into GA as well, as
low-level flow increases into the evening/overnight.

In addition to tornado potential -- including the risk for a couple
of significant tornadoes across a broad area represented by the
ENH/30% risk area, large hail and damaging winds will also occur in
some areas. Risk will continue through the overnight hours,
tapering from west to east across the lower Mississippi Valley but
continuing across the central Gulf Coast states and into the
southern Appalachians through 18/12z.

..Goss.. 03/15/2021

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ACUS03 KWNS 160735
SWODY3
SPC AC 160734

Day 3 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
0234 AM CDT Tue Mar 16 2021

Valid 181200Z - 191200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS EXTENDING FROM
GEORGIA NORTHWARD ACROSS THE CAROLINAS...

CORRECTED TO INCLUDE SIG AREA IN PROB GRAPHIC

...SUMMARY...
Severe weather is expected from southern Virginia southward into
Florida, and westward into portions of eastern Kentucky/eastern
Tennessee Thursday. Along with potential for hail and locally
damaging winds, several tornadoes -- a couple of them possibly
strong -- are anticipated.

...Synopsis...
A vigorous upper low initially progged over eastern portions of the
Ozarks, is expected to continue steady eastward progression through
the period, weakening gradually as it crosses the Appalachians and
reaches Virginia/the Carolinas by the end of the period. In the
wake of this feature, ridging will expand to encompass much of the
country, as an eastern Pacific trough nears the Pacific Northwest
Coast late.

As the upper system advances, a surface low just ahead of cyclone
aloft will likewise progress eastward, crossing the mountains during
the evening before redeveloping offshore through the end of the
period. A trailing cold front will cross the southern Appalachians
through the first half of the period, before moving offshore
overnight. A second day of fairly widespread -- and possibly
locally substantial -- severe risk is anticipated.

...Parts of the Mid and Southern Atlantic Coast states, and westward
into eastern parts of KY/TN...
Showers and thunderstorms -- and some attendant severe weather risk
-- will be ongoing Thursday morning, particularly over the southern Appalachians region. With associated clouds streaming northeastward
across the middle and southern Atlantic Coast states, hindered
heating -- and thus tempered diurnal destabilization -- is expected.
Still, with northward advection of higher theta-e air east of the
mountains ahead of the advancing surface system causing a rapid
retreat of the remnant damming front, sufficient CAPE should evolve
to support vigorous storms -- with intensity of the updrafts aided
by strongly veering/increasing flow with height.

Storms should increase through midday west of the mountains across
parts of eastern Kentucky/eastern Tennessee ahead of the synoptic
system. Relatively low-topped storms -- and local risk for
all-hazards severe weather -- will likely evolve.

Meanwhile, storms are expected to spread across Georgia and into the
Carolinas ahead of the advancing cold front, along with some
pre-frontal cellular development within a zone of strong warm
advection east of the mountains. Given ample instability and a very
favorably sheared environment, relatively widespread and locally
substantial severe weather potential is indicated -- including risk
for a few strong tornadoes. Potential is expected to expand
northward toward/into southern Virginia with time as the front
retreats into the evening, before convection begins to end from west
to east as the cold front moves toward -- and eventually off -- the
Atlantic Coast.

..Goss.. 03/16/2021

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ACUS03 KWNS 170732
SWODY3
SPC AC 170731

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0231 AM CDT Wed Mar 17 2021

Valid 191200Z - 201200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe weather is not expected across the U.S. on Friday.

...Discussion...
As the primary/compact vort max moves off the Carolina/Virginia
coasts early, secondary troughing will move eastward across the
eastern U.S. through the period. The primary cold front -- already
off most of the East Coast Friday morning, will move slowly
southward across Florida through the period. Showers and perhaps a
few lightning strikes may linger near the coastal Carolinas very
early in the period, with a few showers and a thunderstorm also
possible over southern parts of Florida during the day.

In the West, a cold front will advance across the northern
Rockies/Great Basin, as a large upper trough moves gradually inland.
Scattered showers will accompany the inland advance of this system
with sporadic lightning strikes possible in a few areas as well.

..Goss.. 03/17/2021

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ACUS03 KWNS 180731
SWODY3
SPC AC 180729

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0229 AM CDT Thu Mar 18 2021

Valid 201200Z - 211200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe weather is not anticipated over the U.S. on Saturday

...Discussion...
A large upper trough will continue moving across the western U.S.
Saturday, while a second trough lingers over the southeastern
portion of the country. At the surface, high pressure will prevail
east of the Rockies, while a cold front moves across the interior
West in tandem with the upper trough.

Showers and occasional lightning will likely occur across portions
of the interior Rockies, but meager instability suggests weak
convection. Elsewhere, thunderstorms are not expected.

..Goss.. 03/18/2021

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ACUS03 KWNS 190725
SWODY3
SPC AC 190724

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0224 AM CDT Fri Mar 19 2021

Valid 211200Z - 221200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe storms are not expected over the U.S. on Sunday.

...Discussion...
While weak southern-stream troughing continues to linger over the
southeastern U.S., a larger western trough -- comprised of phasing
between shorter-wavelength systems in the northern and southern
streams -- will continue advancing across the western half of the
U.S. through the period.

With time, the faster-moving northern short-wave feature will begin
to separate from its southern-stream counterpart, moving quickly
across the Canadian Prairie and adjacent northern Plains states
through Monday morning. Meanwhile, the slower southern trough may
begin to close off over the New Mexico overnight.

Weak instability -- and correspondingly weak convection -- will
accompany the passage of the southern-stream trough across the
southwestern quarter of the country. Sporadic lightning flashes may
accompany this convection as it spreads across the Four Corners area
through the evening. Overnight, as a low-level jet ramps up over
the southern Plains in response to height falls ahead of the
advancing system, meager elevated destabilization may support
occasional lightning overnight as far east as portions of Kansas and
Oklahoma through the end of the period.

..Goss.. 03/19/2021

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ACUS03 KWNS 210702
SWODY3
SPC AC 210701

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0201 AM CDT Sun Mar 21 2021

Valid 231200Z - 241200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not currently forecast on Tuesday.

...Synopsis...

A negatively tilted upper shortwave trough over the Ozark Plateau
will lift north/northeast to the Great Lakes on Tuesday. Meanwhile,
another shortwave trough will develop southward across the Four
Corners vicinity, maintaining a larger-scale upper trough across the
western two-thirds of the CONUS. A surface low attendant to the
Midwestern upper shortwave trough will develop northeast from
northwest MO to WI, sweeping a cold front across the mid-MS Valley.
The southern extent of the cold front will stall across AR into
eastern and central TX as moderate south/southwesterly deep-layer
flow maintains a warm advection regime across the south-central
states to the Lower MS Valley.

...Central/Northern IL Vicinity..

Surface dewpoints will generally remain in the 40s to low 50s ahead
of the surface low/cold front. Cloud cover and showers also will
limit stronger heating across much of the mid-MS Valley, but
steepening midlevel lapse rates will support at least weak
instability. Moderate shear and strong background flow of around
30-40 kts between 850-700 mb could aid in a few loosely organized
thunderstorms or line segments along the cold front and near the
surface low. Given weak instability and the possibility that
convection could be elevated, any damaging-gust potential appears
conditional, precluding probabilities at this time.

...Lower MS Valley...

Showers and thunderstorms will likely be ongoing Tuesday morning
ahead of the cold front across AR into northern LA and eastern TX.
This activity will continue eastward into MS and southeast LA
through the afternoon. Stronger ascent will quickly be lifting
northeast of the region as the upper trough ejects northeast toward
the Great Lakes. Overall severe potential appears low at this time,
as stronger destabilization will be limited by heavy rain.
Nevertheless, moderate shear and modest lapse rates will overspread
the region, and some gusty winds could accompany any stronger cells.

..Leitman.. 03/21/2021

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ACUS03 KWNS 220646
SWODY3
SPC AC 220645

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0145 AM CDT Mon Mar 22 2021

Valid 241200Z - 251200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN
TEXAS INTO THE LOWER MISSISSIPPI VALLEY...

...SUMMARY...
Isolated severe thunderstorms are possible from eastern Texas into
the Lower Mississippi Valley on Wednesday.

...Synopsis...

There is still quite a bit of uncertainty and spread among various
forecast guidance regarding Wednesday. A broad area of southwesterly
flow will exist from the southern Plains eastward as a shortwave
trough over the Upper Midwest weakens and spreads northeast into
Canada, while another upper shortwave trough ejects eastward from
the Four Corners to the southern Plains by Thursday morning. A
surface trough will develop across central TX while a warm front
lifts northward across LA/MS, and a broad warm sector centered on
the Lower MS Valley will be characterized by mid to upper 60s
dewpoints. The progression of the Texas surface trough/cold front
and the Gulf coast warm front remain uncertain and will have
implications for severe potential on Wednesday into early Thursday
morning.

...Eastern TX to the Lower MS Valley...

A strong warm advection regime will persist across the central Gulf
Coast, and heavy rainfall will likely be the main hazard for the
region during the Day 3 period. However, at least some
low-end/isolated severe thunderstorm potential appears possible.
Ongoing rain and isolated thunderstorms will persist through the
period, limiting stronger heating during the day. However, mid/upper
60s dewpoints beneath moderate midlevel lapse rates will support
MLCAPE as high as 1000-2000 J/kg. At least some weak inhibition will
persist given the lack of stronger heating, and weak subsidence
between the two upper shortwave troughs may suppress organized
severe potential for much of the day. Wind profiles will improve
after peak heating, with effective shear greater than 40 kt
forecast. Upper forcing will remain weak for most of the period
until the western upper shortwave trough kicks out into the Plains
during the last 3-6 hours of the period. As this occurs, a surface
cold front will sharpen and shift east across central/eastern TX.

Overall, the thermodynamic and kinematic environment could support
at least isolated severe potential with all hazards possible.
However, expected heavy rain, weak forcing, and timing of mid/upper
level and surface features is resulting in low confidence. For now,
low-end Marginal severe probabilities will be introduced for a
conditional threat for embedded supercell storms in areas of ongoing precipitation, from Wednesday afternoon into early Thursday morning.

..Leitman.. 03/22/2021

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ACUS03 KWNS 230741
SWODY3
SPC AC 230740

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0240 AM CDT Tue Mar 23 2021

Valid 251200Z - 261200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER A PORTION
OF THE LOWER MISSISSIPPI VALLEY AND SOUTHEAST STATES...

...SUMMARY...
A potential outbreak of severe storms including strong tornadoes,
large hail and damaging wind will exist Thursday afternoon into the
overnight across a portion of the lower Mississippi Valley and
Southeast States.

...Lower Mississippi Valley and Southeast States...

A robust shortwave trough will move from southern TX early Thursday
northeast through the lower MS Valley during the day and into the OH
Valley overnight. Thursday morning a cold front will extend from the
Great Lakes southwest to a weak surface low in eastern TX, then
south into the western Gulf. In response to the ejecting shortwave
trough, the cyclone is forecast to undergo significant deepening as
it develops northeast during the day. A cold front will accelerate
through the lower MS Valley and into the Southeast States, while a
warm front initially from northeast TX into northern LA and central
MS lifts northward to near the TN border by evening.

It is likely that elevated storms will be ongoing in warm advection
regime across northern MS, AL and TN. This activity is expected to
continue lifting northward allowing for destabilization from the
south with time. Rich low-level moisture with upper 60s to near 70 F
dewpoints will advect northward through warm sector contributing to
moderate instability with up to 2000 J/kg MLCAPE. Potential will
exist for discrete storms to develop in the warm sector as the
boundary layer destabilizes during the afternoon. Vertical wind
profiles with very strong shear and large 0-1 km hodographs will
support supercells capable of producing strong tornadoes and large
hail. Activity will spread northeast through the lower MS valley
during the day and into the TN Valley by late afternoon into the
evening. Additional storms may also develop along the cold front
with linear structures capable of damaging wind.

...OH Valley...

Widespread early storms during the first half of the day lower
confidence in more than A SLGT/MRGL risk for this region at this
time. However, some destabilization is expected by late day or
during the evening. Potential will exist for a line of storms to
develop along the cold front with damaging wind and QLCS tornadoes
the main threats. The SLGT risk may need to be expanded farther
north in later outlooks.

..Dial.. 03/23/2021

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ACUS03 KWNS 240730
SWODY3
SPC AC 240729

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0229 AM CDT Wed Mar 24 2021

Valid 261200Z - 271200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A PORTION
OF THE SOUTHEAST STATES AS WELL AS NORTHEAST KANSAS...

...SUMMARY...
A few strong storms will be possible Friday over a portion of the
Southeast States as well as a portion of northern Kansas.

...Carolinas through southern Georgia...

A progressive shortwave trough will continue northeastward into the
Northeast States Friday. A strong low-level jet initially from
eastern NC into the Middle Atlantic will move offshore by mid day.
Tendency will be for the deeper forcing and stronger low-level winds
to lift northeast away from the moist warm sector present across the
Carolinas into the Gulf Coast States. A corridor of modest
instability should evolve in the pre-frontal warm sector in the
presence of strong deep shear. While a few strong storms with
locally strong wind gusts and possibly hail might develop along the
cold front during the day, tendency for low-level winds to veer and
weaken in the presence of only shallow forcing suggests overall
severe threat should remain marginal.

....Lower Mississippi Valley region...

The front will stall along southern portions of the Gulf Coast
States during the day, but should begin to move back northward
during the evening as a southerly low-level jet strengthens.
Destabilization and isentropic ascent resulting from this process
will contribute to the development of mostly elevated storms during
the evening and overnight. A few instances of hail and locally
strong wind gusts might occur with some of this activity.

...North-central through northeast Kansas...

A weak surface low is expected to develop in association with a
minor shortwave trough ejecting northeast through the Central Plains
during the afternoon. Low-level moisture will be limited in this
region, but strong surface heating and steep lapse rates will
contribute to marginal instability. A few strong storms may develop
in the vicinity of a trough/dryline feature and spread east through north-central KS. Strong vertical shear will be present, but
uncertainty regarding amount of destabilization and overall low
confidence in scenario precludes more than a MRGL risk category at
this time.

..Dial.. 03/24/2021

$$
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ACUS03 KWNS 250736
SWODY3
SPC AC 250735

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0235 AM CDT Thu Mar 25 2021

Valid 271200Z - 281200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE LOWER
MISSISSIPPI AND TENNESSEE VALLEYS AS WELL AS THE MIDWEST...

...SUMMARY...
Isolated strong to severe storms are possible Saturday across the
lower Mississippi through Tennessee Valley regions. Other strong to
severe storms are possible across a portion of the Midwest. Isolated
damaging wind and large hail are the main threats.

...Lower Mississippi through Tennessee Valley region...

Some thunderstorms will probably be ongoing early Saturday, mainly
across a portion of the TN Valley. There is some uncertainty
regarding how these early storms evolve, but this activity will
probably shift northeast and weaken with time. Under the influence
of a broad fetch of southwesterly low-level winds, richer moisture
with surface dewpoints in the low to mid 60s F will advect northward
into this region contributing to moderate instability with up to
1500 J/kg MLCAPE. Other storms might develop during the evening or
overnight within the warm advection regime as the low-level jet
strengthens. A cold front associated with a northern stream
shortwave trough will approach this region from the northwest and
likely contribute to the development of additional storms overnight,
likely consolidating into lines and clusters. This activity will be
embedded within strong vertical wind profiles supporting the
potential for a few organized structures capable of mainly isolated
strong to damaging wind gusts and hail.

...Midwest region...

Low-level moisture will be more limited in this region. However,
cold air aloft will compensate and the atmosphere could become at
least marginally unstable as the boundary layer warms during the
afternoon. Storms may initiate along frontal zone within a strongly
sheared environment supportive of a few organized storms capable of
isolated large hail and damaging wind.

..Dial.. 03/25/2021

$$
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ACUS03 KWNS 260732
SWODY3
SPC AC 260730

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 AM CDT Fri Mar 26 2021

Valid 281200Z - 291200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM A PORTION OF
THE SOUTHERN APPALACHIANS INTO THE CAROLINAS AND MIDDLE ATLANTIC...

...SUMMARY...
Strong to severe storms are possible from the Carolinas into the
Middle Atlantic region Sunday afternoon. A few strong to severe
storms will also be possible from the central and southern
Appalachian region into a portion of the Tennessee Valley and
Southeast States.

...Mid Atlantic into the Carolinas...

An intense low-level jet will shift from the southern and central
Appalachians into the Carolinas and Mid Atlantic during the day in
association with a progressive northern-stream shortwave trough. A
warm front will move northward through the Mid Atlantic during the
day prior to the arrival of a cold front. Upper 50s to low 60s F
dewpoints will advect through the warm sector contributing to modest instability as the surface layer warms with up to 1000 J/kg MLCAPE
possible. Thunderstorms are expected to develop along and just ahead
of the cold front as it advances into this region during the late
afternoon and early evening. This activity will be embedded within
strong deep layer wind profiles that will support bowing structures
as well as a few supercells. Damaging wind will be the main threats,
but a few tornadoes and some hail will also be possible before the
front moves offshore during the evening.

...Ohio through Tennessee Valleys and Southeast States...

Thunderstorms will be in progress early Sunday along a cold front
from the OH Valley into a portion of the Southeast States within a
marginally unstable environment. These storms will be embedded
within strong deep layer winds and vertical shear supportive of
embedded organized structures including bowing segments. Some of
this activity will pose an ongoing threat for isolated damaging wind
as it advances east during the morning.

..Dial.. 03/26/2021

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ACUS03 KWNS 270713
SWODY3
SPC AC 270712

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0212 AM CDT Sat Mar 27 2021

Valid 291200Z - 301200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms may develop from Monday into Monday night
across parts of the Southeast. No severe weather is expected.

...Discussion...
A low amplitude upper-level trough is forecast to move across the
western Gulf of Mexico on Monday as a cold front advances southward
into northern Florida. Isolated thunderstorms may develop along the
front during the day on Monday. As the upper-level trough moves
across the central Gulf of Mexico Monday night, weak moisture
advection may take place in the central and eastern Gulf coast
states. Just ahead of the trough, a few thunderstorms may develop
Monday night from southeast Louisiana eastward to southwestern
Georgia. Instability is expected to be weak and no severe weather
threat is expected.

..Broyles.. 03/27/2021

$$
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ACUS03 KWNS 280711
SWODY3
SPC AC 280710

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0210 AM CDT Sun Mar 28 2021

Valid 301200Z - 311200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE ARKLATEX AND LOWER MISSISSIPPI VALLEY...

...SUMMARY...
A marginal threat for damaging wind gusts and hail may develop
across parts of the Arklatex and lower Mississippi Valley Tuesday
night.

...Arklatex/Lower Mississippi Valley...
An upper-level trough is forecast to move across the central and
northern Plains on Tuesday as southwest mid-level flow remains in
place from the southern Plains to the Northeast. At the surface, a
cold front is forecast to advance quickly southeastward into the
Arklatex and mid Mississippi Valley. Ahead of the front, moisture
advection could enable surface dewpoints to reach the lower 60s F
Tuesday night from northeast Texas to northern Mississippi. Model
forecasts suggest that scattered thunderstorm development will be
possible along and ahead of the front, mainly after midnight. MUCAPE
near 1000 J/kg and effective shear around 40 kt, evident on forecast
soundings, would make hail and marginally severe wind gusts
possible.

..Broyles.. 03/28/2021

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ACUS03 KWNS 290707
SWODY3
SPC AC 290706

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0206 AM CDT Mon Mar 29 2021

Valid 311200Z - 011200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE WESTERN GULF COAST...SOUTHEAST...SOUTHERN
APPALACHIANS...CAROLINAS AND VIRGINIA...

...SUMMARY...
Thunderstorm development will be possible on Wednesday from the
western Gulf Coast northeastward into the Carolinas and Virginia.
Strong wind gusts and hail will be the primary threats.

...Western Gulf Coast/Southeast/Southern
Appalachians/Carolinas/Virginia...
An upper-level trough is forecast to move eastward across the
central U.S. on Wednesday. At the surface, a cold front is forecast
to advance southeastward into the southeastern U.S. being positioned
form the western Gulf Coast to the southern Appalachians by midday.
As surface temperatures warm during the day, pockets of weak
instability are expected to develop, with surface dewpoints ahead of
the front in the lower to mid 60s F. Increasing instability and
low-level convergence along and just ahead of the front will likely
result in thunderstorm development during the afternoon. Near the
front, deep-layer shear is forecast to be in the 45 to 55 kt range.
This combined with steep low-level lapse rates will make isolated
damaging wind gusts a possibility. Hail could also occur with the
stronger cores. Any severe threat is expected to be marginal and
confined to the mid to late afternoon when surface temperatures will
be maximized.

..Broyles.. 03/29/2021

$$
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ACUS03 KWNS 310720
SWODY3
SPC AC 310719

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0219 AM CDT Wed Mar 31 2021

Valid 021200Z - 031200Z

...NO THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are not forecast across the contiguous United States
on Friday.

...Synopsis...
A large-scale mid-level trough over the East will slowly move into
the western Atlantic. In its wake, a mid-level ridge will encompass
the western states and overspread the Great Plains. Surface high
pressure will influence conditions across much of the Lower 48.
Dry/stable conditions will likely preclude thunderstorm development.

..Smith.. 03/31/2021

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ACUS03 KWNS 010711
SWODY3
SPC AC 010710

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0210 AM CDT Thu Apr 01 2021

Valid 031200Z - 041200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms are not forecast across the
contiguous United States on Saturday.

...Synopsis...
A broad mid-level ridge will encompass a large part of the West
through the central and northern Great Plains. Farther east, a
mid-level trough will weaken over the western Atlantic to the east
of the Mid-Atlantic/Northeast U.S. A weak mid-level disturbance
initially over NM will move east and weaken as it moves to central
TX by daybreak Sunday. In the low levels, primarily 40s deg F
dewpoints on southeasterly flow will return to the Permian Basin/Big
Bend. A few showers and a couple of high-based thunderstorms are
possible primarily during the late afternoon. Elsewhere, quiescent
conditions will prevail across much of the Lower 48.

..Smith.. 04/01/2021

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ACUS03 KWNS 020715
SWODY3
SPC AC 020714

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0214 AM CDT Fri Apr 02 2021

Valid 041200Z - 051200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not currently forecast across the
contiguous United States on Sunday.

...Synopsis...
A progressive low-amplitude flow pattern will encompass the Lower 48
on Sunday. A mid-level trough is forecast to move southeast from
British Columbia into the Pacific Northwest/northern Rockies as an
area of low pressure develops over the Dakotas. Southerly low-level
flow will advect moisture north through the Great Plains into parts
of the Upper Midwest. Isolated showers and thunderstorms are
possible primarily Sunday evening/night near the terminus of a
developing LLJ within a strengthening warm air advection over the
Upper Midwest.

Farther south, a weakening mid-level disturbance over TX may result
in a few showers and possibly a couple of thunderstorms. However,
thunderstorm coverage is currently expected to remain sparse,
precluding a thunderstorm highlight.

..Smith.. 04/02/2021

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ACUS03 KWNS 030731
SWODY3
SPC AC 030730

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 AM CDT Sat Apr 03 2021

Valid 051200Z - 061200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS CENTRAL AND
SOUTHERN MINNESOTA INTO WESTERN WISCONSIN...

...SUMMARY...
Isolated strong to severe thunderstorms are possible across parts of
the upper Mississippi Valley on Monday.

...Synopsis...
A flattened mid-level ridge is forecast over the MS Valley with
several disturbances located over parts of the West and
south-central Canada. The mid-level trough over Saskatchewan is
forecast to move east into western Ontario during the period and
glance the Upper Midwest. An attendant cold front will push
southeastward across parts of MN into the Dakotas while trailing
westward into parts of the Interior West. The westward extension of
the front will push into the ID/UT/NV vicinity Monday and Monday
night. A pronounced lee trough/dryline will extend from the
southern High Plains to near the CO/KS border by early Monday
evening.

...Upper Midwest...
The northern extent of a warm sector is forecast to destabilize on
Monday as mid-upper 50s dewpoints contribute to a weak to moderately
unstable airmass ahead of a cold front. It appears the cold front
will serve as a focus for scattered showers and thunderstorms to
develop during the afternoon/evening. Steep 700-500 mb lapse rates
7-8 deg C/km owing to cold 500 mb temps (around -18 deg C) will
potentially favor hail growth with the stronger updrafts. If a
cluster can organize during the evening, a wind/hail risk may
persist well after dark as a LLJ strengthens over IA.

...TX-OK Panhandles...
Strong heating is expected to occur over the southern High Plains in
the vicinity of the dryline. Model guidance is currently indicating
only upper 40s to lower 50s dewpoints but very steep low to
mid-level lapse rates will combine to yield 500-1500 J/kg MLCAPE
with a veering wind profile gradually strengthening with height into
the mid levels. Localized erosion of the cap could result in one or
two storms developing during the 21-00z period, but storm coverage
will likely remain very limited if convective initiation occurs.

..Smith.. 04/03/2021

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ACUS03 KWNS 040728
SWODY3
SPC AC 040728

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0228 AM CDT Sun Apr 04 2021

Valid 061200Z - 071200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR CENTRAL KANSAS
INTO SOUTHWEST MISSOURI AND ADJACENT PORTIONS OF OKLAHOMA AND
ARKANSAS...

...SUMMARY...
Severe thunderstorms are possible portions of the central Great
Plains into the western Ozarks late Tuesday afternoon through
Tuesday night.

...Central Great Plains into the Ozarks...
A mid-level low and attendant trough, initially over western WY and
the eastern Great Basin, will move east-southeastward to the central
High Plains. A belt of strong cyclonically curved 500 mb flow will
move through the base of the trough and overspread a destabilizing
warm sector across the central and southern Great Plains. In the
low levels, a surface cyclone over western KS will develop eastward
and elongate as a cold front over the central High Plains surges
southward into northwest TX and the northwest half of OK by early
Wednesday morning.

A capped but gradually moistening boundary layer will spread
northward into northern OK and KS during the day on strengthening
southerly low-level flow. Strong deep-layer ascent near the surface
low will likely favor initial thunderstorm development during the
afternoon. Steep 700-500 mb lapse rates (8-9 deg C/km) and strong
flow will support storm organization with large hail and severe
gusts the primary hazard. A strengthening LLJ during the evening
over OK/KS and associated isentropic lift will probably lead to
additional storms and the organization of a thunderstorm cluster
moving east-southeast during the night into parts of southeast KS
and adjacent parts of OK/AR/MO.

Farther south across OK, thunderstorm development is less likely
during the day owing to the aforementioned cap. Nonetheless, a low
probability scenario for a storm or two southward along the dryline
cannot be ruled out. It seems plausible the risk for isolated to
scattered storms will focus overnight across northern and eastern OK
as strong large-scale forcing promotes isolated to scattered storms.
Hail/wind would be the primary risks with this activity.

..Smith.. 04/04/2021

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ACUS03 KWNS 050717
SWODY3
SPC AC 050716

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0216 AM CDT Mon Apr 05 2021

Valid 071200Z - 081200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR THE ARKLATEX
INTO THE LOWER MISSISSIPPI VALLEY...

...SUMMARY...
Scattered severe thunderstorms are possible across the lower
Mississippi Valley with other isolated severe storms possible
farther north over the middle Mississippi Valley.

...Synopsis...
A neutral-tilt mid-level trough and associated closed low will
slowly move eastward from KS into MO while becoming negatively
tilted by early Thursday. In the low levels, an elongated area of
low pressure centered over KS will develop/deepen as it moves north-northeastward into IA by early evening. A cold front will
progress eastward across the lower MO Valley and Ozarks while an
effective boundary decelerates across the lower MS Valley.

A strong warm conveyer belt Wednesday morning across the Ozarks will
likely lead to widespread clouds and showers/thunderstorms across
much of this area and areas north. Richer low-level moisture
(surface dewpoints in the 60s) will reside across the lower MS
Valley. Heating and a plume of 7-7.5 deg C mid-level lapse rates
will contribute to moderate buoyancy developing (1000-1500 J/kg) in
the Arklatex east to the MS River during the day. Scattered to
widespread thunderstorms coalescing into one or more bands will
likely evolve during the day and push eastward across the MS Valley
during the evening. All hazards will be possible with storms across
the Arklatex due in part to moist low levels co-located with
enlarged hodographs. An eventual transition to a mainly a damaging
wind threat is expected with a tornado risk possibly lingering well
after dark across the lower MS Valley.

Farther north, greater uncertainty exists for severe across parts of
the lower MO Valley during the day in wake of earlier-day
shower/thunderstorm activity. It is possible a bi-modal severe risk
develops via a narrow corridor of destabilization immediately ahead
of the front and focused near the surface low over northwest
MO/southwest IA during the late afternoon. Isolated damaging gusts
appear to be the primary threat across the middle MS Valley later in
the day and into the evening before this activity weakens as it
encounters weaker instability.

..Smith.. 04/05/2021

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ACUS03 KWNS 060729
SWODY3
SPC AC 060728

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0228 AM CDT Tue Apr 06 2021

Valid 081200Z - 091200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR ALABAMA AND
WESTERN GEORGIA WESTWARD INTO THE ARKLATEX...

...SUMMARY...
Isolated severe thunderstorms are possible across the northern Gulf
Coast states on Thursday and Thursday night.

...Synopsis...
A mid-level low will move from northern MO northeastward to WI by
Friday morning. The mid-level height gradient across the lower MS
Valley/Mid South will gradually relax as a belt of strong
west-southwesterly flow weakens during the period. An occluded low
over the Upper Midwest will slowly fill and become increasingly
displaced from a warm sector as frontolysis occurs over the OH
Valley into the Mid South.

...TN Valley westward to the Arklatex...
Showers/thunderstorms will likely be ongoing Thursday morning across
parts of MS/AL/TN within a plume of weak instability (250-750 J/kg
MLCAPE). A linear band of storms will likely push eastward across central-northern AL into eastern TN/western GA during the day, while
slowly weakening as upper support becomes increasingly displaced
from the region. The risk for wind damage may accompany the
stronger storms. Farther north over TN into the OH Valley, scant
instability will likely preclude strong thunderstorm development.

By the late evening into the overnight, strengthening low-level warm
air advection will commence across the Arklatex into the lower MS
Valley. Upwards of 1000-2000 J/kg MUCAPE with 35-40 kt effect shear
may result in elevated strong to locally severe thunderstorms
developing after midnight. Hail is the primary risk but a damaging
gust cannot be ruled out.

..Smith.. 04/06/2021

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ACUS03 KWNS 080729
SWODY3
SPC AC 080728

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0228 AM CDT Thu Apr 08 2021

Valid 101200Z - 111200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR THE NORTHEAST
GULF COAST STATES AND PARTS OF GEORGIA...

...SUMMARY...
Scattered strong to severe thunderstorms are possible across the
northeast Gulf Coast on Saturday.

...MS/AL/GA/FL...
A mid-level disturbance over the Gulf Coast states, to the south of
a potent mid-level trough over eastern KS/MO, will likely support a continuation of an MCS across the Gulf Coast during the morning and
perhaps persisting into the afternoon. A moist and moderately
unstable boundary layer (1000 J/kg MLCAPE) and strong flow, will
favor a risk for damaging winds given the likelihood of a linear
convective mode. Model guidance (particularly the latest ECMWF)
shows this activity moving east over the northeast Gulf Coast. The
northern periphery of the severe risk will probably be constrained
by a transition to weaker instability/less moisture farther
north/northeast across northern and eastern parts of GA.

...TN/KY...
As the primary mid-level shortwave trough moves from eastern KS to
northern IN during the period, strong southerly low-level flow will
transport moisture north during the day to the north/east of an MCS
over the Deep South. A surface low initially over northeast AR will
deepen as it moves to southern Lake Michigan by mid evening.
Widespread clouds will likely limit the amount of surface heating
during the day as a band of showers/thunderstorms on the northern
portion of an MCS moves north-northeast across TN during the
morning. A risk for isolated damaging gusts could continue into the
start of the day-3 period (Saturday morning) and rejuvenate during
the day as the activity spreads northeast towards the OH River.
However, instability will likely remain weak owing to the
aforementioned concern with heating. This activity will likely
weaken by early evening across parts of the OH Valley.

..Smith.. 04/08/2021

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ACUS03 KWNS 100635
SWODY3
SPC AC 100634

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0134 AM CDT Sat Apr 10 2021

Valid 121200Z - 131200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not forecast on Monday.

...Synopsis...

An upper low over the lower Great Lakes will merge with an upper low
migrating eastward across the Upper Midwest/upper Great Lakes region
on Monday. This will maintain strong mid/upper level westerly flow
across the central Plains and Midwest. Further south, low-amplitude
westerly flow will encompass much of the south-central and southeast
U.S. east of the Rockies. Meanwhile, a shortwave trough will develop
southward across the Pacific Northwest/Great Basin vicinity. At the
surface, broad low pressure beneath the upper low over the Great
Lakes will persist. A stalled front near the central Gulf Coast will
lift northward, and moisture will spread across TX and the Lower MS
Valley vicinity ahead of another cold front surging south/southeast
late in the period. A combination of capping and weak forcing will
limit severe potential ahead of the cold front, though showers and
elevated thunderstorms will be possible across parts of the southern
Plains to the Lower MS Valley.

..Leitman.. 04/10/2021

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ACUS03 KWNS 110701
SWODY3
SPC AC 110659

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0159 AM CDT Sun Apr 11 2021

Valid 131200Z - 141200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe thunderstorms are not forecast on Tuesday.

...Synopsis...

The overall pattern will not change much on Tuesday compared to the
Day 2/Monday period. An upper low will continue to deepen and
develop slowly southward over the northwestern U.S. while another
upper low persists over the Great Lakes. This will maintain
low-amplitude westerly flow across the southern tier of the U.S. A
couple of weak perturbations will migrate through this westerly flow
aloft, from the southern Plains to the Lower MS Valley. A stalled
front will extend across southern TX eastward along the central Gulf
Coast vicinity. Surface dewpoints in the 60s will remain over
southern TX, eastward along the Gulf Coast. Weak warm advection will
likely support areas of showers and thunderstorms in the vicinity of
the stalled front. However, inhibition, coupled with weak forcing
and modest deep layer flow, will limit severe potential.

..Leitman.. 04/11/2021

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ACUS03 KWNS 130706
SWODY3
SPC AC 130706

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0206 AM CDT Tue Apr 13 2021

Valid 151200Z - 161200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe storms are not forecast on Thursday.

...Synopsis...

An upper low over the lower Great Lakes region will pivot eastward
to the Mid-Atlantic/Northeast coast by Friday morning. Further west,
the upper low over the Great Basin will become an open wave as it
emerges into the Plains. At the surface, a cold front will extend south/southwest from a low offshore from DE/MD into southern GA and
then likely just offshore the central Gulf Coast and into southern
TX. The front will drop southward across the northern FL Peninsula
while stalling over the northern Gulf. In response to the ejecting
western upper trough, weak lee low development across eastern NM
will result in modest low-level warm advection across TX. While Gulf
moisture will mostly be cut off thanks to the cold front draped over
the region, upper 50s to near 60 F surface dewpoints should work
their way northward toward the Permian Basin after 00z. Showers and
perhaps some elevated thunderstorms will be possible, but severe
potential appears limited by weak instability and a strong cap.

..Leitman.. 04/13/2021

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ACUS03 KWNS 140706
SWODY3
SPC AC 140705

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0205 AM CDT Wed Apr 14 2021

Valid 161200Z - 171200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe storms are not currently forecast on Friday.

...Synopsis...

Moderate westerly deep-layer flow will persist across Texas and the
Gulf Coast states on Friday. An upper shortwave impulse will migrate east/northeast from the central/southern Plains toward the mid-MS
Valley. A weak surface low or trough will progress eastward across
TX and weaken during the day before strong high pressure builds
southward down the Plains. A cold front will push south/southeast
across much of TX during the afternoon and evening, moving offshore
into the Gulf early Saturday morning.

...Southeast TX...

Some strong elevated thunderstorms could develop across parts of
southeast TX during the afternoon/evening, as 7-7.5 C/km midlevel
lapse rates will remain over the region and contribute to weak to
moderate MLCAPE. Forecast guidance varies quite a bit in the
evolution of the surface low/trough across TX and the timing of the
cold front. Additionally, several rounds of thunderstorms are
expected across the region between Day 1/Wed and Day 3/Fri,
resulting in uncertainty in the quality of any warm sector and
possibly outflow boundaries, etc. While some threat for hail or
gusty winds could develop, uncertainty is too high to include
probabilities at this time.

..Leitman.. 04/14/2021

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ACUS03 KWNS 160721
SWODY3
SPC AC 160720

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0220 AM CDT Fri Apr 16 2021

Valid 181200Z - 191200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms appear unlikely across the contiguous
United States on Sunday.

...Synopsis and Discussion...
A belt of strong mid-level westerly flow should be maintained across
much of the lower MS Valley and Southeast on Sunday. At the surface,
high pressure should dominate much of the CONUS. A cold front should
stall and become nearly stationary across the northern FL Peninsula
by Sunday afternoon. With low/mid-level flow largely parallel to the
front, convergence is forecast to remain very weak. Accordingly,
convective development along this boundary appears quite uncertain
on Sunday. Even if storms form across the northern FL Peninsula,
they will probably remain elevated. At this point, the potential for
organized severe storms along/south of the front across the FL
Peninsula appears unlikely given poor low-level convergence and
nebulous large-scale ascent.

Elsewhere, isolated thunderstorms appear possible through the day
across parts of the mid MS Valley in association with a shortwave
trough, and over portions of the southern Rockies and vicinity as
large-scale ascent with a separate upper trough/low overspreads this
region. Very limited instability is expected to preclude a severe
threat for both areas.

..Gleason.. 04/16/2021

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ACUS03 KWNS 170726
SWODY3
SPC AC 170724

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0224 AM CDT Sat Apr 17 2021

Valid 191200Z - 201200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
The potential for severe thunderstorms on Monday across parts of the
central and southern Florida Peninsula appears low at this time.

...Synopsis and Discussion...
Rich low-level moisture will likely remain confined to parts of the
central and southern FL Peninsula to the south of a front on Monday.
Even though instability should increase through the day across this
region, neutral height fields aloft and weak convergence along the
front suggest a fairly limited potential for surface-based storms
and related severe threat across this region. In general, guidance
suggests that the tendency will be for most storms that can form to
remain elevated to the north of the surface boundary.

Farther north, isolated thunderstorms may occur through the day
across parts of eastern NC and southeastern VA as a shortwave trough
moves over this region. Limited low-level moisture and related very
weak instability should preclude a severe threat. Elsewhere,
occasional lightning flashes may also be noted over portions of the
southern High Plains as an upper trough moves eastward, and across
parts of the central Rockies and vicinity as a separate upper trough
digs southward over this area through the period.

..Gleason.. 04/17/2021

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ACUS03 KWNS 180723
SWODY3
SPC AC 180722

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0222 AM CDT Sun Apr 18 2021

Valid 201200Z - 211200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL/SOUTHERN FLORIDA PENINSULA...

...SUMMARY...
Isolated strong to severe storms appear possible on Tuesday across
portions of the central and southern Florida Peninsula.

...Florida Peninsula...
Within large-scale upper troughing across much of the
central/eastern CONUS, a low-amplitude shortwave trough should move
across parts of the Southeast on Tuesday. A persistent surface
boundary across the central FL Peninsula may attempt to lift
northward as a warm front as a weak low develops from the
northeastern Gulf of Mexico to the western Atlantic through the
period. Convection may be ongoing Tuesday morning to the north of
the surface boundary in a modest low-level warm advection regime. It
remains somewhat uncertain how far north the front will advance
across the northern/central FL Peninsula through the day, and this
boundary will likely serve as the northern limit to an isolated
severe threat. With a moist low-level airmass remaining in place
across the central/southern FL Peninsula, it will not take much
diurnal heating to foster weak to locally moderate instability by
Tuesday afternoon. Both low and mid-level wind fields are forecast
to strengthen through the day, supporting strong deep-layer shear.
Organized severe thunderstorms posing mainly an isolated large hail
and damaging wind threat may occur along/south of the front as the
glancing influence of large-scale ascent with the shortwave trough
overspreads this region.

..Gleason.. 04/18/2021

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ACUS03 KWNS 190725
SWODY3
SPC AC 190724

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0224 AM CDT Mon Apr 19 2021

Valid 211200Z - 221200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE MID-ATLANTIC...

...SUMMARY...
Isolated strong to severe storms capable of producing mainly
damaging winds may occur across parts of the Mid-Atlantic on
Wednesday.

...Mid-Atlantic...
Within large-scale upper troughing over the eastern CONUS, a
shortwave trough is forecast to move quickly east-northeastward
across the Mid-Atlantic and over New England on Wednesday. A surface
low initially centered over PA should likewise develop northeastward
into southern New England by Wednesday afternoon while deepening. An
attendant cold front will sweep eastward across the Mid-Atlantic
through the day. Modest low-level moisture return should occur ahead
of this cold frontal passage, with low to mid 50s surface dewpoints
possible per consensus of latest guidance. Diurnal heating across
the warm sector should foster the development of weak instability by
late Wednesday morning. Even though MLCAPE may only reach about
250-500 J/kg ahead of the front, it should be sufficient to support surface-based storms. Current expectations are for a low-topped
convective line to develop along the cold front by early Wednesday
afternoon. These storms should move quickly eastward in tandem with
the cold front, and off the Atlantic Coast by late afternoon or
early evening. Given the forecast strength of the low/mid-level flow accompanying the shortwave trough, isolated strong to damaging wind
gusts appear possible with this line where enough destabilization
can occur.

...South Florida...
A cold front should progress southward across this region through
the period. Large-scale ascent and stronger mid-level flow
associated with upper troughing over the eastern states is expected
to remain well north of the southern FL Peninsula. Given that
low-level winds are forecast to veer to westerly early in the
period, convergence along the front will likely remain quite weak.
Therefore, the potential for organized severe thunderstorms
currently appears low.

..Gleason.. 04/19/2021

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ACUS03 KWNS 200726
SWODY3
SPC AC 200725

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0225 AM CDT Tue Apr 20 2021

Valid 221200Z - 231200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Severe storms are not forecast across the contiguous United States
on Thursday.

...Synopsis and Discussion...
A positively tilted upper trough should move eastward across the
Great Basin and Southwest on Thursday. Large-scale ascent preceding
this feature will encourage lee cyclogenesis across the
southern/central High Plains, with a low-level mass response
occurring over a greater portion of the southern/central Plains
through the period. A southerly low-level jet across these regions
will aid in the transport of Gulf moisture northward across TX and
into OK by late Thursday night. Most guidance indicates that the
airmass across this region will remain capped as an EML advects
eastward from the higher terrain of the Southwest and northern
Mexico. Still, low-level warm advection should increase Thursday
evening/night as the low-level jet gradually strengthens. Elevated
storms may occur in this regime on a fairly isolated basis. Although instability will be increasing as this warm advection process
occurs, it will likely remain too weak to support a large hail
threat with any storms that can form.

Elsewhere, isolated storms may occur Thursday across coastal south
FL in the vicinity of a remnant front, and over parts of the eastern
Great Basin and central Rockies in association with the upper
trough. Other occasional lightning flashes appear possible across
portions of the northern Rockies and vicinity as a separate
shortwave trough overspreads this region. Weak instability across
all these areas should preclude any severe risk.

..Gleason.. 04/20/2021

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ACUS03 KWNS 210729
SWODY3
SPC AC 210728

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0228 AM CDT Wed Apr 21 2021

Valid 231200Z - 241200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE
SOUTHERN PLAINS INTO THE LOWER MISSISSIPPI VALLEY...

...SUMMARY...
Isolated to scattered severe thunderstorms should occur Friday into
Friday night from parts of the southern Plains into the lower
Mississippi Valley. Large to very large hail, damaging winds, and
isolated tornadoes all appear possible.

...Synopsis...
An upper trough should eject eastward from the Four Corners region
and Southwest across the southern/central Plains on Friday,
eventually reaching the lower/mid MS Valley by the end of the
period. An EML with associated steep mid-level lapse rates will
likely be present over much of OK/TX. A low-level jet should
continue to transport low-level moisture northward through the day
across the southern Plains, with a warm front potentially reaching
as far north as the OK/KS border vicinity. At the surface, a weak
low over the TX Panhandle Friday morning is forecast to develop
southeastward to the vicinity of southwestern OK/western north TX by
Friday evening while gradually deepening. A dryline should extend
southward from this low across portions of west/central TX. The
surface low should continue developing eastward to the lower MS
Valley late Friday into early Saturday morning, with a composite
dryline/cold front sweeping eastward across central/east TX. Rich
low-level moisture should advance northward ahead of the low/front
across much of LA and southern MS late in the period.

...Southern Plains...
Large-scale ascent associated with the shortwave trough should
overspread the warm sector across OK/TX by late Friday morning into
the early afternoon. As the cap erodes, robust convective
development appears likely along the eastward-mixing dryline. There
is still some uncertainty regarding the position of the dryline by
Friday afternoon across the southern Plains. Regardless, the
presence of rather steep mid-level lapse rates, increasing low-level
moisture, and diurnal heating should support moderate to locally
strong instability across the warm sector in OK/TX by Friday
afternoon. Deep-layer shear across this region appears strong enough
to support organized severe thunderstorms, including supercells.
Current expectations are for convection to initially develop along
or just east of the dryline, and subsequently move
east-northeastward. Large hail appears likely with this initial
activity, and isolated very large hail (2+ inch diameter) may also
occur. A veering/strengthening wind profile suggests some threat for
isolated tornadoes with any storms that can remain semi-discrete
through early Friday evening. Eventually, upscale growth may occur
along the cold front, with a damaging wind threat potentially
continuing into parts of east TX late Friday. Other isolated severe
storms may develop in the low-level warm advection regime in the
open warm sector along parts of the middle/upper TX Coast into east
TX through the day, posing a risk for all severe hazards.

...Sabine River Valley into the Lower Mississippi Valley...
A south-southwesterly low-level jet is forecast to strengthen
considerably from east TX into LA and southern MS Friday
evening/night. Surface-based convection appears increasingly
probable across this area as low-level moisture quickly increases.
The EML may advect eastward over this region, and NAM forecast
soundings show a favorable thermodynamic and kinematic environment
to support organized severe thunderstorms along/south of the warm
front. All hazards, including tornadoes, will be possible through
Friday night into early Saturday morning. The best severe threat may
be focused with the eastward-developing low-level jet, but
additional severe storms along the cold front may also occur. Even
with this seemingly favorable setup for severe thunderstorms, the
potential exists for afternoon storms with low-level warm advection
to slow the northward advance of the warm front and limit
instability. Once uncertainty regarding the evolution of these
afternoon storms is better resolved, greater severe probabilities
for tornadoes may need to be included for parts of the Sabine River
Valley vicinity.

..Gleason.. 04/21/2021

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ACUS03 KWNS 220729
SWODY3
SPC AC 220728

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0228 AM CDT Thu Apr 22 2021

Valid 241200Z - 251200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHEAST...

...SUMMARY...
Isolated to scattered severe thunderstorms may occur Saturday across
parts of the Southeast. All severe hazards appear possible,
including large hail, damaging winds, and a few tornadoes.

...Southeast...
An upper trough should continue moving eastward from the lower/mid
MS Valley across the Southeast and Mid-Atlantic on Saturday. A
strong south-southwesterly low-level jet is forecast to advance
quickly eastward from AL Saturday morning across GA and into SC by
the afternoon. At the surface, a weak low over the lower MS Valley
and Mid-South should develop northeastward towards the central
Appalachians during the day, with some uncertainty whether it
deepens substantially or not. Regardless, rich low-level moisture
should move northward across AL/GA/SC, supporting a threat for
surface-based thunderstorms.

Strong to severe convection may be ongoing Saturday morning from
portions of southern LA into MS and AL in association with the
low-level jet. As this activity spreads eastward through Saturday
afternoon, it may continue to pose at least an isolated severe
threat so long as it does not outpace the low-level moisture return.
A rather strong mid-level jet attendant to the upper trough will
support similarly strong deep-layer shear. Forecast soundings across
the warm sector in GA/SC from both the 00Z NAM and ECMWF show a veering/strengthening wind profile with height through mid levels,
potentially supporting supercells. Some eastward advection of an EML
from the Plains also appears possible across the warm sector, which
combined with the increasing low-level moisture and diurnal heating
should foster moderate to locally strong instability along/south of
the warm front.

All severe hazards, including the potential for a few tornadoes,
appear possible given the favorable thermodynamic and kinematic
environment forecast as thunderstorms move eastward across the
Southeast through the afternoon and early evening. The main
uncertainties are the possible limiting effect of morning convection
on the development of instability, and predominant storm mode.
Finally, there also appears to be a conditional threat for severe
thunderstorms behind the initial morning activity across southern LA
into MS/AL, as strong instability should develop ahead of an
eastward-moving cold front. However, low-level flow is forecast to
quickly veer to westerly behind the passage of the previously
mentioned low-level jet. This should limit convergence along the
front, and the most pronounced large-scale ascent associated with
the upper trough should be mostly east of this region by Saturday
afternoon. Even so, if convection can develop in this regime, then
both isolated large hail and damaging winds would be possible.

..Gleason.. 04/22/2021

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ACUS03 KWNS 230657
SWODY3
SPC AC 230656

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0156 AM CDT Fri Apr 23 2021

Valid 251200Z - 261200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms are possible across the Florida Peninsula as
well as southern portions of the Pacific Northwest. No severe
thunderstorms are currently forecast.

...Synopsis...
A pair of low-amplitude shortwave troughs are expected to move off
the Mid-Atlantic and Southeast coasts, respectively, early Sunday.
In the wake of these shortwaves, predominantly zonal flow is
forecast to persist across the central and eastern CONUS throughout
much of day. Upper ridging will begin to build over the central
CONUS Sunday evening, as a deepening shortwave trough moves into the
western Great Basin and another moves into southern CA.

At the surface, a low attendant to the Mid-Atlantic shortwave trough
will likely be centered just off the Delmarva Peninsula early Sunday
morning. A cold front will extend southwestward from this low across
northern FL. Expectation is for this front to become increasingly
diffuse as it slowly moves southward across the FL Peninsula. Even
so, ample low-level moisture ahead of the front should result in
enough buoyancy for isolated thunderstorms. High pressure will
dominant sensible weather for remainder of the central and eastern
CONUS, limiting thunderstorm potential.

Only other location where thunderstorms appear possible is over central/southern OR and adjacent portions of northern CA. Here,
ascent and cool mid-level temperatures attendant to the shortwave
moving into the western Great Basin could result in isolated
lightning flashes.

..Mosier.. 04/23/2021

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ACUS03 KWNS 240724
SWODY3
SPC AC 240724

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0224 AM CDT Sat Apr 24 2021

Valid 261200Z - 271200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms are possible across the Upper Midwest as well
as over portions of the northern and central Rockies on Monday. An
isolated storm or two is also possible across southern Florida.

...Synopsis...
Upper pattern is expected to undergo significant amplification on
Monday as western CONUS upper troughing deepens and downstream upper
ridging builds. Strong mid-level flow will exist throughout the
basal portion of the upper trough and extend from northern Mexico
across the central Plains into the Upper Midwest throughout much of
the period. Strengthening of this mid/upper flow is anticipated late
in the period over the southern High Plains.

This persistent southwesterly flow aloft will encourage deepening
surface pressure across the central Plains with a resulting increase
in southerly winds across much of the southern/central Plains and
Lower/Mid MS Valley. These surface wind will couple with a strong
low-level jet to foster robust moisture advection throughout the
period.

Some early day thunder is possible ahead of a deepening low-level
cyclone moving from central ND into western/northwestern MN.
Additional isolated thunderstorms are possible across the Upper
Midwest Monday evening into early Tuesday morning as a low-level jet dynamically strengthens and the cyclone matures. Additionally, a
cold front is forecast to gradually shift southeastward across
southern WI, western/central NE, and northeast IA during the
afternoon and evening. Warm mid-level temperatures are currently
expected to preclude development along this front, but forecast
soundings reveal that a slight increase in temperatures and/or
dewpoint could result in convective initiation. The environment
supports severe thunderstorms with any deep convection, and severe probabilities may be needed in later outlooks if initiation appears
more probable.

Lastly, isolated thunderstorms are possible over portions of the
northern and central Rockies as the upper trough and attendant cold
mid-level temperatures move through the region.

..Mosier.. 04/24/2021

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ACUS03 KWNS 250724
SWODY3
SPC AC 250723

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0223 AM CDT Sun Apr 25 2021

Valid 271200Z - 281200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF
WEST TX AND THE TX PANHANDLE INTO WESTERN/CENTRAL OK AND
SOUTH-CENTRAL KS....

...SUMMARY...
Severe thunderstorms are possible Tuesday afternoon through Tuesday
night from portions of West Texas and the Texas Panhandle into
western/central Oklahoma and south-central Kansas.

...Synopsis and Discussion...
A deep upper trough is forecast to be in place over the western
CONUS early Tuesday morning. Strong mid/upper level flow will extend
throughout the basal portion of this trough, beginning the period
arced from off the central CA coast across northern Mexico and into
the southern High Plains. This upper trough is expected to make
modest eastward progress throughout the day while an embedded
shortwave trough ejects over northern/central NM into eastern
CO/western KS. This evolution will help spread the strong mid-level
flow over much of the southern and central Plains.

The surface pattern early Tuesday will likely feature a low near the
central NE/KS border, with a dryline extending south-southwestward
across central KS and northwest OK, and into the TX Panhandle. This
dryline will likely remain in place, sharpening throughout the day
as moderate low-level moisture advection continues to its
east/southeast. Low-level convergence into this boundary combined
with increasing large-scale ascent attendant to the approaching
shortwave is forecast to result in convective initiation amid a
diurnally destabilizing air mass. Some uncertainty exists regarding
storm coverage, largely as a result of unknown cap strength and
quality of the moisture return. Even so, environmental conditions
support a predominantly supercell mode with any storms that do
develop. All severe hazards are possible, including very large hail
and tornadoes.

Central High Plains surface cyclogenesis will likely cause a
westward retreat of the dryline during the evening. At the same
time, a strengthening low-level jet will increase warm-air advection
across the boundary. These factors are expected to result in
additional storm development from the Permian Basin into
south-central KS. Primary threat with these evening and overnight
storms is large hail.

..Mosier.. 04/25/2021

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ACUS03 KWNS 260731
SWODY3
SPC AC 260730

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 AM CDT Mon Apr 26 2021

Valid 281200Z - 291200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE
SOUTHERN PLAINS THROUGH THE MID MS VALLEY...

...SUMMARY...
Isolated severe thunderstorms are possible from the southern Plains
through the Middle Mississippi Valley on Wednesday.

...Synopsis and Discussion...
Southern-stream upper trough is forecast to move eastward throughout
the day, ending the period extended from southwest KS through
northern Mexico and phased with a northern-stream upper trough. This
evolution will allow strong southwesterly flow aloft to persist over
northern Mexico and the southern Plains while also expanding
northeastward through the Mid MS Valley and into the middle OH
Valley.

Surface pattern early Wednesday morning will feature a cold front
extending from a low over southern Lower MI southwestward to another
low over western KS early Wednesday morning. A dryline is forecast
to extend from the western KS low southward into southwest TX. This
cold front will move southeastward throughout the day while
gradually overtaking the dryline from northwest to southeast.

A broad area of low severe potential will extend throughout the warm
sector in the vicinity of the front from central OK into western IN.
In this region, persistent warm-air advection will likely allow the thunderstorm cluster ongoing over OK Wednesday morning to progress northeastward throughout the day. Cloudiness associated with this
cluster will limit destabilization but robust vertical shear could
still result in a few stronger storms capable of hail.

Farther south (from southwest/south-central OK southward through the
TX Hill County), afternoon storm development appears possible along
the dryline/cold front as these boundaries move
eastward/southeastward. However, evolution of Tuesday night's
thunderstorms will impact overall likelihood for development as well
the most probable locations for initiation. Any residual outflow
boundaries would also play an important role for afternoon storm
development. Given that these mesoscale details are uncertain at
this forecast range, only 5%/Marginal probabilities were introduced
with this outlook. Higher probabilities may be needed in later
outlooks as these details become more predictable.

..Mosier.. 04/26/2021

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ACUS03 KWNS 270721
SWODY3
SPC AC 270721

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0221 AM CDT Tue Apr 27 2021

Valid 291200Z - 301200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE OH VALLEY...

...SUMMARY...
Isolated strong to severe thunderstorms are possible across the
middle and upper Ohio Valley on Thursday.

...Synopsis...
A northern-stream shortwave trough is forecast to extend from
northwest Ontario into central KS early Thursday morning. A
southern-stream upper low will likely be centered over the southern
High Plains at the same time. The northern-stream system is expected
to remain progressive throughout the day, moving through the Upper
MS Valley, Upper Great Lakes, and much of the OH Valley. In
contrast, the southern-stream system is only expected to make
minimal eastward progression, likely ending the period centered over
the Big Bend region of TX.

A surface low associated with the northern-stream shortwave is
expected to be centered over the Mid MS Valley early Thursday,
before then quickly progressing northeastward throughout the day. As
it moves northeastward, an attendant cold front will sweep
southeastward through the Mid MS and OH Valleys. Low to mid 60s
dewpoints will likely precede this front across the OH Valley,
contributing to modest instability despite poor mid-level lapse
rates and abundant cloud cover. Moderate to strong mid-level flow
will also be in place over the OH Valley, with the resulting
environmental conditions that could support a few strong to severe
storms. Damaging wind gusts and/or a brief tornado are the primary
threats.

..Mosier.. 04/27/2021

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ACUS03 KWNS 280723
SWODY3
SPC AC 280722

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0222 AM CDT Wed Apr 28 2021

Valid 301200Z - 011200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms are possible Friday across much of the
Southeast. Isolated thunderstorms are also possible across south
Texas late Friday night/early Saturday morning.

...Synopsis...
A surface low will likely be centered just off the New England coast
early Friday. A cold front is forecast to extend southwestward from
this low into NC and then west-southwestward across the Southeast
states to another low over central LA. This front is expected to
make slow southward progress across the Southeast, contributing to
isolated thunderstorms as it encounters a moist and modestly buoyant
air mass. Limited buoyancy is currently expected to keep the severe
threat low.

Upper low over Mexico will likely begin moving eastward late Friday
night. Resulting increase in ascent downstream across south TX may
aid in isolated thunderstorm development late Friday night/early
Saturday morning.

..Mosier.. 04/28/2021

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ACUS03 KWNS 290724
SWODY3
SPC AC 290723

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0223 AM CDT Thu Apr 29 2021

Valid 011200Z - 021200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM
SOUTHEAST/EAST TEXAS INTO NORTHWEST LOUISIANA...

...SUMMARY...
Isolated severe thunderstorms are possible Saturday into early
Sunday from southeast/east Texas into northwest Louisiana.

...TX Hill Country into the Lower MS Valley...
An upper low will likely be located over northern Mexico early
Saturday morning. This low is forecast to slowly progress
northeastward throughout the day, while also becoming increasingly
negatively tilted. Moderate flow aloft will persist through the base
of this upper cyclone throughout the day, spreading along the TX
Gulf Coast and into the Lower MS Valley. Widespread cloudiness and
numerous showers and thunderstorms will likely accompany this system
as it moves northeastward. Poor lapse rates and limited heating will
temper buoyancy, but vertical shear will strong enough to support a
few more organized updrafts, particularly as the low-level flow
increase late Saturday night/early Sunday morning. This late-period
increase in low-level flow could also act in tandem with the
negative tilt of the upper trough to promote upscale growth into
more of a forward-propagating convective line.

...Elsewhere...
A few lightning flashes may occur from the northern Rockies into the
central High Plains as a low-amplitude shortwave trough traverses
the region. Isolated thunderstorms are also possible from southern
MN into Lower MI, as isentropic ascent increases Saturday night
across a warm front extending from south-central NE into southern
WI.

..Mosier.. 04/29/2021

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ACUS03 KWNS 300731
SWODY3
SPC AC 300730

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 AM CDT Fri Apr 30 2021

Valid 021200Z - 031200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SUNDAY INTO SUNDAY
EVENING ACROSS PARTS OF SOUTHEAST TEXAS...SOUTHERN AND EASTERN
LOUISIANA...MUCH OF MISSISSIPPI AND ADJACENT PORTIONS OF WESTERN
ALABAMA AND SOUTHWESTERN TENNESSEE...

...SUMMARY...
Severe thunderstorms are possible Sunday into Sunday evening across
much of the lower Mississippi Valley.

...Synopsis...
A couple of significant short wave perturbations are forecast to
remain progressive within a southern branch of split mid-latitude
westerlies across the central and southern tier of the U.S. Models
indicate that the lead impulse will lose amplitude as it accelerates northeastward in negatively tilted fashion, into a more broadly
confluent regime across and northeast of the lower Mississippi
Valley. This will coincide with the increasing amplification of the
evolving upstream mid-level troughing, which is forecast to dig
southeastward through much of the Four Corners states by late Sunday
night.

Preceding the trailing perturbation, a broadening plume of warm and
capping elevated mixed-layer air is forecast to overspread much of
the southern Great Plains. Cold surface ridging appears likely to
nose southward to the lee of the northern Rockies in the wake of the
lead southern branch impulse, and mid-level troughing digging within
the northern branch. Within broad surface troughing shifting
southeastward ahead of the cold air, the more prominent surface low
is expected to migrate southeastward across the Texas Panhandle
vicinity into western portions of northern Texas by 12Z Monday. It
appears that this will be accompanied by an increasing influx of
low-level moisture beneath the warming mid-levels, across the
southern Great Plains into lower Mississippi Valley.

...Upper Texas coast into lower Mississippi Valley...
Models continue to indicate a window of opportunity for vigorous
convective development in advance of the eastward advecting plume of
elevated mixed-layer air. Ahead of the remnant mid-level cold core
of the lead perturbation, a cluster of thunderstorms may be
spreading across the upper Texas coast vicinity into Louisiana early
in the period. This may be in the process of weakening, with
activity tending to progress into an initially cooler/drier
low-level environment associated with surface ridging across and
east of the lower Mississippi Valley. However, most model output
does suggest that a modest (30-40 kt around 850 mb) southerly
low-level jet preceding this convection will supported elevated
moisture return across much of southern/eastern Louisiana and
Mississippi. And guidance suggests that daytime heating and
downward mixing of this moisture will contribute to a destabilizing
boundary layer through Sunday afternoon.

A zone of enhanced lower/mid tropospheric warm advection in the
immediate wake of the lead perturbation may provide one focus for
vigorous new thunderstorm development across southern Louisiana
during the day Sunday. This forcing could support an upscale
growing and organizing cluster of storms, aided by strong deep-layer
supported by an associated 50 kt southwesterly 500 mb jet. If this
does not negatively impact areas to the north, other thunderstorm
development may increase by Sunday afternoon along the axis of
destabilization through Mississippi. This may be initially
discrete, but convection may tend to grow upscale along outflow
spreading northeastward from the storm cluster to the south.

Aided by the development of moderate CAPE, strong shear and
lingering relatively cool mid-levels, supercell structures capable
of producing severe hail, damaging surface gusts and perhaps a few
tornadoes appear possible.

..Kerr.. 04/30/2021

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ACUS03 KWNS 010731
SWODY3
SPC AC 010730

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 AM CDT Sat May 01 2021

Valid 031200Z - 041200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE MONDAY TROUGH
MONDAY NIGHT ACROSS PARTS OF THE LOWER OHIO VALLEY INTO OZARK
PLATEAU AND ADJACENT PORTIONS OF THE SOUTHERN GREAT PLAINS...

...SUMMARY...
Severe thunderstorms are possible, particularly Monday evening into
the overnight hours, in a corridor from the the lower Ohio Valley
through the Ozark Plateau and adjacent portions of the southern
Great Plains. Some of this activity may pose a risk for large,
damaging hail and strong wind gusts.

...Synopsis...
Models suggest that the leading edge of large-scale mid-level
ridging, in a southern branch of split mid-latitude westerlies, may
begin to build inland across California and Baja during this period.
As this occurs, initially amplified downstream troughing is forecast
to shift east of the Four Corners states and northern Mexican
Plateau. Rather than as one strong, consolidated perturbation, it
appears that a series of smaller-scale impulses will emerge, but the
broader cyclonic regime may come in phase with troughing in the
northern branch, east of the Rockies into an increasingly confluent
regime across and east of the Mississippi Valley.

While there is model consensus, in a broad sense, concerning this
general pattern evolution, quite a bit of spread is evident among
the output concerning the synoptic and sub-synoptic scale
developments. However, it does appears that a frontal zone within
broad surface troughing will progress east-southeast of the Upper
Midwest/Great Lakes region and central Great Plains, preceded by an
influx of seasonably high boundary-layer moisture content, on
seasonably strong west-southwesterly low-level flow.

...Ohio Valley/Ozark Plateau and adjacent southern Great Plains...
Due to the large spread among the various deterministic model
output, placement of severe probabilities is largely based on the
overly smoothed out mean ensemble output of the various models.
However, there appears reasonable agreement that a general corridor
from eastern Oklahoma into the lower Ohio Valley may become a focus
for intense convective development by early Monday evening and
continue into the overnight hours.

Of particular concern, it appears that moderate to strong potential
instability will develop across this region during the day, as mid
60s to near 70F surface dew points advect northeastward ahead of the
front, beneath east-northeastward advecting elevated mixed-layer
air. This likely will occur in the presence of at least 30-50 kt west-southwesterly deep layer mean flow, with more than sufficient
deep-layer shear to support organized convective development. A few
supercells are possible, but large-scale forcing for ascent
associated within interacting perturbations within the flow probably
will support rapid upscale growing clusters.

By Monday evening, it is possible that the most significant impulse
emerging from the Southwest may be a prominent contributor to this
forcing, across the Ozark Plateau vicinity, before spreading toward
the lower Ohio Valley. Given the environment, large, damaging hail
appears possible, particularly in the early storm development, with
the risk for severe wind gusts becoming more prominent as activity
consolidates and organizes.

..Kerr.. 05/01/2021

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ACUS03 KWNS 020731
SWODY3
SPC AC 020730

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 AM CDT Sun May 02 2021

Valid 041200Z - 051200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS TUESDAY ACROSS THE
LOWER MISSISSIPPI VALLEY INTO THE TENNESSEE VALLEY...CUMBERLAND
PLATEAU AND PARTS OF THE SOUTHERN APPALACHIANS...

...SUMMARY...
Widespread strong to severe thunderstorm development is possible
Tuesday from the lower Mississippi and Ohio Valleys into the
Allegheny and Cumberland Plateau regions. This will include a risk
for large hail, damaging wind gusts and perhaps a couple of
tornadoes.

...Synopsis...
Models indicate that mid-level ridging will continue to build across
the Pacific Northwest and British Columbia through this period, on
the leading edge of an amplified belt of westerlies across the
northern mid-latitude Pacific. It appears that downstream flow will
remain at least somewhat less amplified. However, there may be some consolidation of mid-level troughing across and east of the
Mississippi Valley, associated with the east-northeast acceleration
of the remnants of larger-scale troughing emerging from the
Southwest, to the south of a broadening mid-level low evolving near/
south of Hudson Bay.

In response to these developments, a significant cold front is
forecast to advance east of the Mississippi Valley, toward the
Appalachians, and off the northwestern Gulf Coast. There remains
considerable spread within the various model output concerning
possible cyclogenesis along the front, from portions of the Mid
South through the lower Great Lakes region and Quebec. However,
seasonably high boundary-layer moisture content ahead of the front,
in the presence of strengthening southwesterly deep-layer mean wind
fields, may contribute to a risk for severe storms Tuesday into
Tuesday evening.

...Mississippi Valley into Appalachians...
Due to continuing large spread within the model output, the details
of the potential convective evolution for this period remain rather
uncertain. An organized convective system, or its remnants, may be
ongoing across parts of the lower Ohio Valley at the outset of the
period. It is possible that this could spread, with at least some
lingering risk for severe wind and hail, across the mid and upper
Ohio Valley early in the day. However, this may occur prior to
arrival of the more substantive low-level Gulf moisture return, and
it remains unclear what influence this will have on subsequent
destabilization ahead of the cold front, upstream, during the day.

There is considerable signal in the model output that large-scale
forcing for ascent may contribute to increasingly widespread
thunderstorm development across the lower Mississippi Valley early
in the day. And associated convective overturning may tend to
quickly stabilize initially steep lower/mid tropospheric lapse rates
associated with a plume of elevated mixed-layer air. However, aided
by boundary-layer dew points around 70 F, remnant instability
probably will remain sufficient to support a risk for organized
severe thunderstorm development. In the presence of seasonably
strong shear, convection capable of producing large and damaging
wind gusts appears possible, with at least some risk for a couple of
tornadoes.

..Kerr.. 05/02/2021

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ACUS03 KWNS 030730
SWODY3
SPC AC 030729

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0229 AM CDT Mon May 03 2021

Valid 051200Z - 061200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS WEDNESDAY ACROSS
PARTS OF THE MIDDLE AND SOUTH ATLANTIC SEABOARD...

...SUMMARY...
Strong thunderstorms may impact parts of the middle and south
Atlantic Seaboard on Wednesday, with at least some storms posing a
risk for severe weather.

...Synopsis...
Mid-level ridging, on the leading edge of an amplified belt of
westerlies emanating from the northern mid-latitude Pacific, may
shift inland of the Pacific Northwest/British Columbia coast during
this period, as upstream mid-level troughing approaches coastal
areas. However, blocking may become a bit more prominent in the
downstream flow, and a broadening mid-level low centered near James
Bay may move little through this period. At least a couple of short
wave impulses digging to the lee of the ridging may contribute to
the maintenance of broad cyclonic flow to the south of the mid-level
low, across the U.S. Great Plains into Mississippi Valley. Models
indicate that this regime will expand a bit farther eastward
Wednesday, as remnant perturbations, emerging in prior days from the
Southwest, progress across the Atlantic Seaboard.

One of these perturbations probably will be accompanied by a belt of strengthening southwesterly lower/mid tropospheric flow across parts
of the mid and south Atlantic Seaboard, ahead of a composite cold
front initially approaching the Appalachians by 12Z Wednesday. In
response to cyclogenesis across the northern Mid Atlantic into New
England coastal vicinity, the surface cold front is generally
forecast to advance into and across the middle and south Atlantic
Seaboard late Wednesday into Wednesday night.

...Middle/South Atlantic Seaboard...
Seasonably moist boundary-layer air advecting northward ahead of the
cold front, coinciding with the strengthening southwesterly
pre-frontal wind fields, will contribute to at least a conditional
risk for severe thunderstorm development Wednesday. However,
convective overturning associated with widespread thunderstorm
development Tuesday into Tuesday night probably will tend to
stabilize upstream mid-level lapse rates. And the extent of
influence of any associated lingering cloud cover and precipitation
on destabilization aided by insolation east of the Appalachians on
Wednesday remains unclear. Given these issues, coupled with
substantive continuing spread among the models concerning the
synoptic and sub-synoptic developments, uncertainties still appear
too large to allow for more than 5 percent severe probabilities at
this time. However, this could change in subsequent outlooks for
this time period.

..Kerr.. 05/03/2021

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ACUS03 KWNS 040729
SWODY3
SPC AC 040728

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0228 AM CDT Tue May 04 2021

Valid 061200Z - 071200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THURSDAY ACROSS
PARTS OF NORTHERN FLORIDA AND EASTERN PORTIONS OF THE FLORIDA
PENINSULA...

...SUMMARY...
Strong thunderstorms may impact parts of northern Florida and
Atlantic coastal portions of the Florida peninsula Thursday, a few
of which may pose at least some risk for large hail and damaging
wind gusts.

...Synopsis...
While upstream flow over the northern mid-latitude Pacific trends
more zonal during this period, models suggest that mid-level ridging
and troughing on the leading edge of this regime will remain
amplified. Eastward progress of the troughing inland of the Pacific
coast, and the ridging across the Rockies, will be slowed, as
blocking in the downstream flow (centered near the Labrador Sea)
persists.

A broad and deep mid-level closed low is forecast to remain centered
near James Bay, with troughing to its south amplifying east of the
lower Mississippi Valley in response to at least a couple of digging
short wave impulses. Models indicate that this will be accompanied
by substantive lower/mid tropospheric drying as far south and east
as the northern Gulf of Mexico, central portions of the Florida
peninsula and the Atlantic waters off the south Atlantic coast by
late Thursday night.

Destabilization, largely supported by seasonably strong mid-level
cooling across parts of the middle Mississippi into lower Ohio and
Tennessee Valleys, as well as across parts of the northern U.S.
intermountain region, aided by surface heating, may contribute to a
risk for thunderstorms during the day. Steepening lapse rates
associated with seasonably strong daytime heating may also
contribute to some risk for thunderstorms across the southern
Rockies, aided by orographic forcing. Seasonably high
boundary-layer moisture content will largely be confined to ahead of
a surface frontal zone advancing southward into the Florida
peninsula.

...Florida...
Models suggest that the front, or a pre-frontal convective outflow
boundary, initially extending across northern Florida early
Thursday, may become a focus for increasing forcing for ascent by
early afternoon. It appears that this will be supported by
increasingly cyclonic and difluent mid/upper flow, in the presence
of modestly steep low-level lapse rates, convective instability and
CAPE on the order of 1000+ J/kg. Beneath 30-40+ kt westerly flow in
the 700-500 mb layer, the environment might become at least
marginally conducive to organized storms capable of producing severe
hail and damaging wind gusts.

Wind fields will be weaker, but with pronounced veering with height
along the sea breeze near or inland of the Atlantic coast, where
low-level convergence will become focused Thursday afternoon. In
the presence of somewhat steeper low-level lapse rates and larger
CAPE, a supercell or two might not be out of the question.
Otherwise, stronger storm development may become capable of
producing strong downbursts, before diminishing/spreading offshore
Thursday evening.

..Kerr.. 05/04/2021

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ACUS03 KWNS 050728
SWODY3
SPC AC 050727

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0227 AM CDT Wed May 05 2021

Valid 071200Z - 081200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE FRIDAY
AFTERNOON AND EVENING ACROSS PARTS OF SOUTHEASTERN
COLORADO...SOUTHWEST KANSAS AND THE TEXAS/OKLAHOMA PANHANDLE
VICINITY...

...SUMMARY...
A couple of strong thunderstorms may impact a small portion of the
central Great Plains late Friday afternoon and evening, posing some
risk for severe hail and strong surface gusts.

...Synopsis...
Models suggest that a blocking mid-level high, centered over the
Labrador Sea, will be maintained through this period. It appears
that this will continue to preclude the eastward progression of the
broad mid-level low to its west-southwest. However, there may be
some southward redevelopment of the circulation center to the west
and southwest of James Bay, in response to a perturbation pivoting
around its periphery. And large-scale mid-level troughing to its
south, initially encompassing much of the eastern U.S., may begin to de-amplify, as a consolidating short wave impulse accelerates east-northeastward across the southern Mid Atlantic coast into the
western Atlantic. It appears that this will occur as ridging within
the southern branch of splitting upstream flow overspreads the
central and southern Great Plains, in advance of elongating
large-scale mid-level troughing progressing across the Intermountain West/Rockies.

In lower-levels, substantive lower/mid tropospheric drying may
continue through much of the northern and eastern Gulf of Mexico,
across the remainder of the Florida peninsula, and well east of the
Atlantic Seaboard. Despite deepening surface troughing east of the
Colorado Front Range into south central portions of the Great
Plains, substantive low-level moistening from the western Gulf of
Mexico may only reach the lower Rio Grande Valley vicinity by late
Friday night. However, steep lapse rates, aided by insolation
beneath a plume of seasonably cold mid-level air across parts of the
East, and aided by seasonable surface heating beneath cooling aloft
across parts of the Intermountain West into Rockies, will contribute
to the risk for thunderstorms Friday into Friday night.

...Parts of central Great Plains...
In the presence of steepening lower/mid tropospheric lapse rates,
various model output suggests that boundary-layer moistening
associated with evaporation/transpiration may contribute to CAPE on
the order of 500-1000 J/kg by late Friday afternoon. It appears
that this will become focused near/east of a developing surface low
within lee surface troughing, where low-level convergence and
low/mid-level warm advection may support scattered thunderstorm
development. Deep-layer shear, largely due to pronounced veering of
winds with height in low to mid-levels, may become sufficient to
support a supercell structure or two. Severe hail and localized
strong surface gusts appear the primary potential hazards, and
activity could grow upscale into a small organized cluster before
weakening late Friday evening.

..Kerr.. 05/05/2021

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ACUS03 KWNS 070725
SWODY3
SPC AC 070724

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0224 AM CDT Fri May 07 2021

Valid 091200Z - 101200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
CENTRAL/EAST TEXAS TO THE MID-SOUTH...

...SUMMARY...
Isolated to scattered severe storms appear possible on Sunday from
parts of central/east Texas to the Mid-South.

...Southern Plains to the Mid-South and Lower Ohio Valley...
A low-amplitude shortwave trough should advance from the
southern/central Plains to the lower/mid MS Valley and lower OH
Valley through Sunday evening. A weak surface low over southwestern
MO Sunday morning is forecast to develops towards the lower OH
Valley in the same time frame, while a trailing cold front moves
southeastward across parts of central/east TX, AR, and the
Mid-South. A strong southwesterly low-level jet is forecast to shift
quickly eastward from the Mid-South vicinity to the OH Valley by
Sunday afternoon.

Mainly elevated storms will probably be ongoing Sunday morning
across portions of southern MO/IL in the warm advection regime
associated with the low-level jet. In the wake of this early
activity, low-level moisture should increase ahead of the
southeastward-moving cold front. Mid to upper 60s surface dewpoints
appear likely to be in place across much of the warm sector by
Sunday afternoon. Diurnal heating of this moist low-level airmass
should foster moderate to potentially strong instability ahead of
the front, particularly across central/east TX into parts of
northern LA and much of AR. Even though large-scale ascent across
this region may remain fairly muted, most guidance indicates
convection will develop along the cold front. Forecast deep-layer
shear appears strong enough to support organized severe storms, with
both large hail and damaging straight-line winds possible. Upscale
growth into a line along the front may also occur. These storms
should eventually weaken with eastward extent across the lower MS
Valley as they outpace the better low-level moisture return and
encounter a less unstable airmass.

Farther north across parts of the mid MS Valley into the Lower OH
Valley, instability should be weaker owing to the influence of the
morning convection and slightly less low-level moisture return.
Still, the presence of low to perhaps mid 60s surface dewpoints
along and just east of the weak surface low suggest some potential
for surface-based convection across this region. Various forecast
soundings indicate strong shear in the low levels, but weak to
minimal instability. Although some severe threat may materialize
across parts of southern IL/IN into western/central KY Sunday afternoon/evening, this potential currently appears too limited to
include any more than a Marginal Risk for these areas.

..Gleason.. 05/07/2021

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ACUS03 KWNS 090729
SWODY3
SPC AC 090728

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0228 AM CDT Sun May 09 2021

Valid 111200Z - 121200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN PLAINS INTO THE LOWER MISSISSIPPI VALLEY AND
SOUTHEAST...

...SUMMARY...
Isolated strong to severe storms may occur Tuesday across parts of
the southern Plains into the lower Mississippi Valley and Southeast.

...Southern Plains into the Lower Mississippi Valley and
Southeast...
Mainly elevated storms should be ongoing at the start of the period
Tuesday morning across parts of the southern High Plains as a weak, low-amplitude shortwave trough overspreads this region. Steep
mid-level lapse rates associated with an EML will probably still be
present across much of TX downstream of this early day convection.
Moderate elevated instability and sufficient deep-layer shear
appears to be present across this region, and isolated large hail
may occur with any supercells that can develop and persist. Storms
should eventually cross a surface front, with increasing potential
for becoming surface based through the afternoon across parts of
central into coastal/east TX. The stronger west-southwesterly winds
aloft will likely remain to the north of this region, but enough
mid-level flow should be present to support some updraft
organization and continued isolated severe potential.

Farther east, a surface front should move only slowly southward
through the day across LA into central and southern MS/AL/GA.
Although details regarding convective evolution remain unclear, it
does appear that diurnal heating of a moist low-level airmass to the
south of the front will support weak to moderate instability by
Tuesday afternoon. Mid-level flow should not be overly strong across
the warm sector, but it may still be enough to foster storm
organization. One or more clusters may form along the front and move south-southeastward through Tuesday evening, posing a threat for
isolated large hail and damaging winds.

..Gleason.. 05/09/2021

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ACUS03 KWNS 110727
SWODY3
SPC AC 110726

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0226 AM CDT Tue May 11 2021

Valid 131200Z - 141200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms appear unlikely across the contiguous
United States on Thursday.

...Synopsis and Discussion...
A shortwave trough is forecast to move from the lower/mid MS Valley
across the Southeast on Thursday. Surface high pressure should
remain prominent over much of the central/eastern CONUS, with a
front extending over the Gulf of Mexico and the vicinity of northern
FL. Rich low-level moisture will likely remain confined to locations along/south of this boundary through the period. Convection should
develop across parts of the FL Peninsula through the day, but the
stronger mid-level flow associated with the shortwave trough will
probably be displaced generally north of the surface front. Although
a strong storm or two may occur across some portion of the FL
Peninsula Thursday afternoon given the moderate instability
forecast, deep-layer shear currently appears too marginal to include
low severe probabilities.

Other storms may occur across parts of the northern and central
Plains in association with a southwesterly low-level jet and related
warm advection. Moisture should remain quite limited across this
region owing to the frontal intrusion over the Gulf of Mexico, and
instability is likewise forecast to remain weak. Elsewhere, isolated
storms appear possible Thursday across parts of the southern High
Plains as modest low-level moisture returns, and across parts of the
northern Rockies and adjacent High Plains as a weak mid-level
perturbation traverses this area.

..Gleason.. 05/11/2021

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ACUS03 KWNS 120727
SWODY3
SPC AC 120726

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0226 AM CDT Wed May 12 2021

Valid 141200Z - 151200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN/CENTRAL PLAINS...

...SUMMARY...
Isolated strong to severe storms appear possible across parts of the southern/central Plains on Friday.

...Southern/Central Plains...
West-northwesterly mid-level flow should continue Friday across
parts of the southern/central Plains, with modestly stronger winds
forecast in a fairly narrow belt from CO/WY into KS/NE and vicinity.
Partially modified Gulf moisture will continue returning northward
over the southern/central Plains through the day, but it should be
fairly shallow across the High Plains. A weak surface low should
develop by Friday afternoon over southeastern CO and vicinity, with
a dryline/lee trough extending southward from this low across the
southern High Plains. Very steep mid-level lapse rates forecast to
be present over the warm sector by peak afternoon heating, coupled
with the modestly increasing low-level moisture, should support the
development of moderate instability in a narrow corridor from
east-central CO into western KS and parts of the OK/TX Panhandles.

However, two limiting factors may tend to temper the magnitude and
coverage of severe storms. The first is the lack of obvious
large-scale forcing for ascent aloft, as mid-level heights should
remain neutral at best, with shortwave ridging otherwise persisting
over the southern Rockies/High Plains. The second is relatively
modest mid-level flow, which may limit deep-layer shear and storm
organization to some extent. Still, there is enough signal for
convective precipitation in guidance near and east of the surface
low and dryline Friday afternoon/evening to include 5% severe
probabilities. Any storms that form in this environment could pose
an isolated hail and strong/gusty wind threat given the steep
low/mid-level lapse rates expected. A southerly low-level jet is
forecast to strengthen Friday evening across this region, but
increasing convective inhibition with eastward extent across the southern/central Plains will probably limit the overall severe
threat farther east into KS/OK.

..Gleason.. 05/12/2021

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ACUS03 KWNS 130729
SWODY3
SPC AC 130728

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0228 AM CDT Thu May 13 2021

Valid 151200Z - 161200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN/CENTRAL PLAINS...

...SUMMARY...
Isolated severe thunderstorms may develop Saturday across portions
of the southern/central Plains.

...Southern/Central Plains...
A closed upper low should move slowly southward across CA on
Saturday, with downstream shortwave ridging persisting over the southern/central Rockies and High Plains. Low-level moisture is
expected to gradually increase across the southern/central Plains
through the period, but it should still be fairly limited for this
time of year. At the surface, a weak low may deepen slightly through
the day across part of the southern/central High Plains, with a
dryline/lee trough extending southward from this low over the
southern High Plains. A warm front should be located across parts of
KS by Saturday evening.

Mid-level flow is forecast to remain rather weak across much of the
warm sector, with marginally stronger winds aloft in a narrow
corridor from eastern CO into KS and vicinity. Modest effective bulk
shear may temper the overall severe threat to some degree. But,
there will likely be steep mid-level lapse rates emanating from an
EML across the southern/central High Plains. These lapse rates
coupled with diurnal heating of the gradually moistening low-level
airmass should support the development of moderate to potentially
strong instability along/east of the surface low and dryline.

Another source of uncertainty is the lack of obvious large-scale
ascent to foster convective initiation, as weak upper ridging should
be located over the warm sector. Still, storms forming over the
higher terrain of the southern/central Rockies will probably spread
eastward through the day, and should eventually encounter a more
unstable airmass. Weak low-level upslope flow in central/eastern CO
may also serve as a forcing mechanism for convective initiation.
Other storms may form along the dryline/lee trough. Although
low/mid-level winds should remain generally weak through the day,
increasing high-level flow may support some venting at anvil level,
and semi-organized clusters capable of producing both isolated large
hail and damaging winds appear possible as they move generally
eastward through the early evening. A southerly low-level jet is
forecast to strengthen Saturday evening across southern KS into
northern OK, and this feature may support a continued isolated
severe threat with any storms that can form/persist in the warm
advection regime.

..Gleason.. 05/13/2021

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ACUS03 KWNS 150647
SWODY3
SPC AC 150646

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0146 AM CDT Sat May 15 2021

Valid 171200Z - 181200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN AND CENTRAL HIGH PLAINS...

...SUMMARY...
Thunderstorms associated with isolated large hail and wind damage
will be possible on Monday across parts of the southern and central
High Plains.

...Southern and Central High Plains...
A shortwave ridge will move eastward through the southern and
central Plains on Monday as an upper-level trough moves across
northern Mexico. At the surface, a low is forecast to deepen in west
Texas during the day with moisture advection continuing across much
of the southern Plains. A west Texas dryline is again forecast to
take shape by afternoon with convection initiating to the east of
the dryline. Scattered thunderstorms should develop and move
east-northeastward across the Texas Panhandle and northwest Texas
during the late afternoon, reaching western Oklahoma and possibly
central Oklahoma during the evening.

NAM forecast suggest that instability will be stronger in the
southern Plains on Monday than on previous days. This is because
surface dewpoints are forecast to increase into the mid to upper 60s
F to the east of the dryline. In addition, mid-level flow is
forecast to strengthen across much of west Texas as the shortwave
trough approaches. Forecast soundings suggest that 0-6 km shear
could reach 40 kt across the Texas Panhandle, where supercells with
large hail will be possible. The models also develop a 35 to 45 kt
low-level jet across northwest Texas early Monday evening. For this
reason, low-level shear should become strong enough for tornadoes.
The more dominant supercells could produce a tornado or two. Wind
damage will also likely accompany any storm clusters that can become
organized.

...Southwest, Central and North Texas...
Mid-level flow across the southern Plains will become
west-southwesterly on Monday as an upper-level trough moves across
northern Mexico. At the surface, dewpoints are forecast to be in the
upper 60s F to lower 70s F across much of southwest, central and
northern Texas. In response, moderate to strong instability is
forecast to develop by afternoon. Convective coverage should remain
isolated during the afternoon, mainly due to a lack of large-scale
ascent. If isolated thunderstorm development can take place, the
strong instability and moderate deep-layer shear would support an
localized severe threat. Strong wind gusts and hail would be the
primary threats.

..Broyles.. 05/15/2021

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ACUS03 KWNS 160729
SWODY3
SPC AC 160728

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0228 AM CDT Sun May 16 2021

Valid 181200Z - 191200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
TEXAS INTO PARTS OF WESTERN AND SOUTHERN OKLAHOMA...

...SUMMARY...
Strong thunderstorms will be possible across much of Texas into
parts of Oklahoma on Tuesday. A few storms may become severe with a
threat of large hail and damaging wind gusts.

...Synopsis...
An upper low forecast to be centered somewhere near the southern
Rockies at the start of the period is forecast to weaken and eject northeastward through the day Tuesday, as an upper ridge continues
to build over the eastern CONUS. A weak surface low is forecast to
remain in place over some portion of west TX, with multiple
convectively modulated surface boundaries likely to be located
somewhere over the southern/central Plains.

...TX/OK...
With multiple rounds of convection expected prior to the D3/Tuesday
period across the southern/central Plains, confidence is quite low
regarding the details of any severe thunderstorm threat. A cluster
of convection (potentially posing some threat of hail/wind) may be
ongoing at the start of the period across some portion of southwest
into central/north TX. Difluent upper flow and continued low-level
moisture transport will likely sustain convection through most of
the day across TX into portions of OK.

The greatest relative severe risk will likely evolve along the
southern and western fringe of the more widespread convection, where
stronger destabilization will be possible in the vicinity of a weak
dryline and any outflow boundaries. Midlevel flow/deep-layer shear
to the east of the ejecting upper low/trough will likely be
sufficient to support some organized storm structures, with a risk
of hail, damaging wind, and possibly a tornado with the strongest
convection.

Given the uncertainty, a broad Marginal Risk has been included with
this outlook, with the expectation that some portion of the area
could eventually be upgraded (or possibly downgraded) as details
become clearer.

..Dean.. 05/16/2021

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ACUS03 KWNS 170723
SWODY3
SPC AC 170721

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0221 AM CDT Mon May 17 2021

Valid 191200Z - 201200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN AND CENTRAL PLAINS...

...SUMMARY...
Thunderstorms associated with hail and marginally severe wind gusts
will be possible on Wednesday across parts of the southern and
central Plains.

...Texas Coastal Plains...
An upper-level trough is forecast to move into the southern High
Plains on Wednesday. Mid-level flow ahead of the upper-level tough
will be south-southwesterly across much of the southern Plains. An
MCS may be ongoing at the start of the period across parts of
south-central and east-central Texas. To the southeast of the MCS, a
moist airmass should be in place with surface dewpoints near 70 F.
In response, moderate instability is expected to develop across much
of the Texas Coastal Plains by midday. Convective development will
be possible along an outflow boundary associated with the ongoing
MCS. The forecast position of this outflow boundary is highly
uncertain at this time. The NAM keeps the outflow boundary further
west, which would be a more favorable scenario for severe storm
development. In contrast, the GFS drives the outflow boundary
southeastward across much of the Texas Coastal Plains. This would be
a less favorable scenario for severe storms, because much of the
airmass would be worked over by afternoon. If the NAM scenario pans
out, low to mid-level flow is forecast to be strong enough for
organized severe storms. The primary threats would be for isolated
damaging wind gusts and hail. Due to the conditional nature of the
forecast, a slight risk will not be added at this time.

...Southern and Central High Plains...
An upper-level trough is forecast to move into the southern and
central High Plains on Wednesday. In response, a lee trough will
likely strengthen across the High Plains, resulting in moisture
advection during the day. Surface dewpoints from the Texas Panhandle
northward into western Kansas should rise into the lower to mid 60s
F, contributing to pockets of moderate instability. Thunderstorm
development will be possible during the afternoon along the western
edge of a north-to-south corridor of instability. These storms are
forecast to move across the Texas Panhandle and western Kansas
during the late afternoon and early evening. Although supercells can
not be ruled out, most of the convection should remain
multicellular. Hail and strong gusty winds are expected to be the
primary threats.

..Broyles.. 05/17/2021

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ACUS03 KWNS 180718
SWODY3
SPC AC 180717

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0217 AM CDT Tue May 18 2021

Valid 201200Z - 211200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL AND NORTHERN HIGH PLAINS...

...SUMMARY...
Severe thunderstorms with large hail and wind damage will be
possible on Thursday across parts of the central High Plains.
Marginally severe thunderstorms may occur outside of the slight risk
area in parts of the High Plains.

...Central and Northern High Plains...
An upper-level low will be in place across the western states on
Thursday as divergent south-southwesterly mid-level flow takes shape
over the Rockies. At the surface, a lee trough will deepen across
eastern Colorado and eastern Wyoming with southeasterly winds
advecting low-level moisture northwestward toward the foothills of
the Front Range and Medicine Bows. As surface temperatures warm,
convection will likely initiate in the higher terrain, with
thunderstorms moving eastward across the central High Plains during
the afternoon. Moderate instability combined with 30 to 40 kt of
deep-layer shear will be favorable for severe storms. As cells move
away from the foothills, supercell development with large hail and
wind damage will be possible. An isolated tornado threat will also
be possible. The severe threat should persist into early evening
with a gradual transition to linear mode.

Further north into northeast Wyoming and southeast Montana, a
north-northwest to south-southeast corridor of moderate instability
is forecast to develop by Thursday afternoon. Convection will likely
initiate in the higher terrain and move northeastward into the
northern High Plains during the afternoon. Moderate deep-layer shear
should support severe storm development. Supercells with isolated
large hail will be possible. However, the degree of instability that
develops will be more uncertain than in areas further to the south.
A slight risk appears warranted, especially if moderate instability
does develop across much of the northern High Plains, as some of the
model solutions are suggesting.

..Broyles.. 05/18/2021

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ACUS03 KWNS 190706
SWODY3
SPC AC 190705

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0205 AM CDT Wed May 19 2021

Valid 211200Z - 221200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL TO NORTHERN HIGH PLAINS AND UPPER MIDWEST...

...SUMMARY...
Thunderstorms associated with hail and strong gusty winds will be
possible Friday in the central and northern High Plains and into the
Upper Midwest.

...Central and Northern High Plains...
An upper-level low will remain in place across the Intermountain
West on Friday with south to south-southwesterly mid-level flow in
the Rockies and High Plains. A moist airmass will be in place
throughout much of the Great Plains. The western edge of the moist
airmass will be located in the central High Plains, where surface
dewpoints should be in the lower to mid 50s F. In response to
surface heating, a pocket of moderate instability is forecast to
develop by afternoon from northeast Colorado into western Nebraska.
Convection that initiates in the higher terrain of northeast
Colorado and southeast Wyoming will move northeastward into this
pocket of instability during the afternoon. MLCAPE in the 1500 to
2000 J/kg range along with 30 to 40 kt of 0-6 km shear would support
an isolated severe threat. If these conditions materialize, then
supercells with large hail and wind damage would be possible during
the late afternoon. There is some uncertainty concerning how much
instability will increase and the models could be overdone. For this
reason, will keep the threat level at marginal for now.

...Upper Midwest...
An upper-level ridge will be in place across the Ohio and Tennessee
Valleys on Friday as mid-level flow remains south-southwesterly
across the Great Plains and Upper Midwest. A corridor of maximized
low-level moisture is forecast from far northeast Kansas into
central and northern Wisconsin. As surface temperatures warm during
the day, weak instability is expected to develop. Thunderstorm
development will be supported by a belt of enhanced low-level flow
located along the moist corridor. Scattered thunderstorms are
forecast to move northeastward along this corridor during the late
afternoon and early evening. The instability combined with around 30
kt of deep-layer shear would be sufficient for a marginal wind
damage and hail threat.

..Broyles.. 05/19/2021

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ACUS03 KWNS 200556
SWODY3
SPC AC 200555

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
1255 AM CDT Thu May 20 2021

Valid 221200Z - 231200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN HIGH PLAINS...

...SUMMARY...
Thunderstorms associated with marginally severe wind gusts and hail
will be possible in the southern High Plains on Saturday.

...Southern High Plains...
An upper-level low will remain over the Intermountain west on
Saturday with mid-level flow from the south to south-southwest
across the Rockies and High Plains. Flow at the surface is forecast
to be from the southeast across much of the southern Plains, which
will advect low-level moisture westward into west Texas and eastern
New Mexico. Surface dewpoints could reach the upper 50s to near 60 F
across parts of west Texas and eastern New Mexico. In response, a
pocket of moderate instability may develop by Saturday afternoon.
Thunderstorm development appears likely in the higher terrain of
eastern New Mexico, to the west of this pocket of instability. These
storms should move northeastward into the southern High Plains
during the afternoon. NAM forecast soundings for 00Z/Sunday in
eastern New Mexico show MLCAPE near 1200 J/Kg with 0-6 km shear at
40 kt. This combined with steepening low-level lapse rates during
the mid to late afternoon could support a marginal wind damage
threat. Hail will also be likely in the stronger cores. At this
time, the amount of instability that is forecast is too weak to
warrant issuing a slight risk.

..Broyles.. 05/20/2021

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