ACUS48 KWNS 180750
SWOD48
SPC AC 180749

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0249 AM CDT Thu Sep 18 2025

Valid 211200Z - 261200Z

...DISCUSSION...
An upper shortwave trough is forecast to move across the northern
Rockies on Day 4/Sun while low-amplitude, broad upper troughing
persists across the central portion of the CONUS. By Day 5/Mon, the
northern Rockies upper trough is expected to rapidly deepen as it
overspread the plains. Rich boundary layer moisture if forecast to
be in place across portions of the southern/central Plains into the
MS Valley as a strong cold front moves across parts of the Plains.
While the timing of the upper trough ejecting into the Plains is
uncertain, some severe potential could develop on Day 5/Mon across
the southern/central Plains toward the Mid/Lower MO Valley.
Uncertainty remains too high to include 15 percent probabilities at
this time however.

Beyond Day 5/Mon, uncertainty increases as large spread among model
guidance persists with regard to the evolution of a developing upper
low somewhere over the mid-section of the CONUS into Day 8/Thu.
Severe potential is uncertain, and the overall pattern may favor
heavy rain over organized severe heading into Day 6/Tue, but model
trends will continue to be monitored.

..Leitman.. 09/18/2025

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ACUS48 KWNS 030817
SWOD48
SPC AC 030816

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0316 AM CDT Fri Oct 03 2025

Valid 061200Z - 111200Z

...DISCUSSION...
A cold front is forecast to move east across much of the Midwest and Northeast/Mid-Atlantic vicinity through Day 6/Wed. This could result
in increasing thunderstorm potential ahead of this feature given a
moist prefrontal boundary layer. Most guidance suggests instability
will be limited however, likely due to a combination of weak lapse
rates and areas of cloudiness/showers ahead of the front. Severe
thunderstorm potential appears low.

Further west, the ECMWF suite of guidance suggests an upper
shortwave trough may eject across the central Rockies into the
central Plains around Day 6 or 7/Wed or Thu, with some southerly
return flow bringing Gulf moisture northward ahead of this feature.
However, the GFS suite of guidance is delayed with this feature
until near/after Day 8/Fri. Thunderstorm could increase across parts
of the Plains late in the forecast period, but uncertainty/model
spread is quite large.

..Leitman.. 10/03/2025

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ACUS48 KWNS 200848
SWOD48
SPC AC 200846

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0346 AM CDT Sat Sep 20 2025

Valid 231200Z - 281200Z

...DISCUSSION...
A complex, low-predictability upper pattern will exist next week and
should eventually evolve into a closed upper low somewhere across
the eastern CONUS by the end of the week. The operational ECMWF and
GFS have significantly different evolution of the upper pattern,
almost switching places from the solution each showed 24 hours ago.
The ECMWF is now more progressive with a large cutoff low from the
GFS by Wed/D5 and Thu/D6. Even the EPS and GEFS (which showed
similar 500mb solutions 24 hours ago) have diverged and have lead to
increasing predictability concerns. Therefore, beyond Day 4, some
severe weather chances are possible within the warm sector ahead of
a surface front. However, significant differences in timing and
evolution of the pattern cast uncertainty on the overall threat.

...Day 4/Tuesday...
As the stronger mid-level trough emerges across the Plains Monday
night, a low-level jet will strengthen across Oklahoma. Therefore, a
MCS will likely be ongoing at 12Z Tuesday in the Oklahoma vicinity.
Moderate destabilization is forecast to the south of the remnant
MCS/outflow boundary on Tuesday. This region will likely be the
focus for some severe weather threat. It is unclear how the
Monday/D3 convection will evolve and how that may impact Tuesday,
but there is some potential for severe storms Tuesday
afternoon/evening. Once the evolution of the mid-level trough and
location of Monday night convection becomes more clear, severe
weather probabilities may be needed.

..Bentley.. 09/20/2025

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ACUS48 KWNS 270845
SWOD48
SPC AC 270843

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0343 AM CDT Sat Sep 27 2025

Valid 301200Z - 051200Z

...DISCUSSION...
Potential Tropical Cyclone Nine may approach coastal South Carolina
early in the period, before probably stalling near or offshore, then accelerating away from the coast into the western Atlantic. This is
likely to be influenced by some combination of a lingering frontal
zone near the Carolina coast, an initial increasing proximity of
Humberto to its east, and cool surface ridging building across the
Northeast through the lee of the Appalachians, in the wake of an
amplifying mid-level trough off the north Atlantic coast during the
early to middle portion of next week. However, even if it does
migrate inland at some point, as some model output indicates is at
least possible, probabilities for the inland advection of a
sufficiently moist and buoyant boundary layer to support an
appreciable risk for tornadoes still appears low.

Otherwise, developments within the westerlies off the mid-latitude
Pacific into North America remain unclear through the latter portion
of the coming week into next weekend. Guidance now appears to
indicate a more amplified regime, including one or more short wave perturbations emerging from evolving large-scale troughing across
the West. However, a slow to develop moist return flow off the Gulf
into the interior U.S. may continue to preclude an appreciable risk
for organized severe thunderstorm development.

..Kerr.. 09/27/2025

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ACUS48 KWNS 050818
SWOD48
SPC AC 050816

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0316 AM CDT Sun Oct 05 2025

Valid 081200Z - 131200Z

...DISCUSSION...
Surface high pressure is forecast to build across portions of the
Midwest and Eastern U.S. behind a cold frontal passage on Day
4-5/Wed-Thu. This high pressure will remain in place for much of the
period, and with the cold front developing south toward the Gulf
coast states, continental low-level trajectories east of the MS will
result in a mostly stable airmass.

Some southerly return flow is possible across the southern/central
Plains late in the period beneath an upper ridge as surface lee
troughing develops ahead of an upper trough developing southeast
across parts of the Plains into the eastern half of the CONUS.
However, severe potential appears low as any strong large-scale
ascent and increasing deep layer shear will remain displaced from
better boundary layer moisture.

..Leitman.. 10/05/2025

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ACUS48 KWNS 060808
SWOD48
SPC AC 060806

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0306 AM CDT Mon Oct 06 2025

Valid 091200Z - 141200Z

...DISCUSSION...
Upper ridging will persist over the Plains through at least Day
5/Fri, while upper troughing develops over the East. Surface high
pressure and a cold front offshore the Atlantic and Gulf coasts will
preclude severe thunderstorm potential due to a mainly dry and
stable airmass east of the Rockies.

By Day 6/Sat and beyond, most medium-range guidance depicts a more
progressive upper pattern, with one or more upper troughs developing
across the West and into the Plains. As this occurs, surface lee
troughing and cyclogenesis over the northern Plains late in the
period should allow for some meager Gulf return flow/increasing
moisture. However, severe potential still appears low given any more appreciable moisture return likely will still be offset from
stronger deep-layer flow and large-scale ascent focused over the central/northern Plains.

..Leitman.. 10/06/2025

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ACUS48 KWNS 070805
SWOD48
SPC AC 070803

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0303 AM CDT Tue Oct 07 2025

Valid 101200Z - 151200Z

...DISCUSSION...
Upper ridging will persist over the Plains on Day 4/Fri. By Day 5 or
6/Sat or Sun, most medium-range guidance depicts an upper shortwave
trough ejecting from a larger-scale western U.S. trough across the
northern Plains. Surface high pressure over the eastern half of the
U.S. prior to this will limit boundary layer moisture and thus,
severe storm potential. However, by the end of the period, spread in
forecast guidance increases. The GFS shows a much more progressive
pattern, bringing an upper trough and cold front across much of the
Plains early next week, with little Gulf return flow to support
severe potential ahead of the front. The ECMWF is slower with the
eastward progression of the western U.S. trough, allowing for more
southerly return flow and increasing moisture across the Plains. If
this occurs, some severe potential could increase early next week.
However, given large uncertainty, predictability is too low.
Regardless, a pattern change toward early next week appears evident
for the Plains.

..Leitman.. 10/07/2025

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ACUS48 KWNS 080811
SWOD48
SPC AC 080810

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0310 AM CDT Wed Oct 08 2025

Valid 111200Z - 161200Z

...DISCUSSION...
An upper ridge over the Plains on Day 4/Sat will shift eastward
toward the Mid/Lower MS Valley on Day 5/Sun as an upper shortwave
trough over the Great Basin ejects northeast across the
northern/central Plains. Surface cyclogenesis will deepen across the
Dakotas as this occurs, and a cold front will sweep east across the northern/central Plains to the Upper Midwest by early Day 6/Mon.
Modest boundary layer moisture will be in place ahead of the cold
front, with severe potential likely limited by weak instability and
poor lapse rates.

Spread among medium range guidance increases by Days 6-8/Mon-Wed.
Some guidance maintains a upper trough/closed low over the eastern
U.S. early next week, maintaining an upper ridge over the central
U.S. while another trough deepens over the west. Other guidance is
more progressive, with the eastern trough moving offshore, allowing
the western trough will sweep east into the Plains by the end of the
period. Regardless of the exact evolution that unfolds, southerly
low-level flow across the Plains will allow for at least modest
moisture return into the southern/central Plains, increasing
thunderstorm potential. However, uncertainty precludes severe
probabilities at this time.

..Leitman.. 10/08/2025

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ACUS48 KWNS 090809
SWOD48
SPC AC 090807

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0307 AM CDT Thu Oct 09 2025

Valid 121200Z - 171200Z

...DISCUSSION...
An upper anticyclone is forecast to remain over TX for much of the
Day 4-8 period, with attendant upper ridging oscillating between the
Plains and the MS Valley. An upper shortwave trough over the Rockies
on Day 4/Sun will lift northeast across the northern Plains into
Canada, along with a deepening surface low. As this occurs, a cold
front will sweep east across the northern/central Plains and the
Upper Midwest through Day 5/Mon. Modest boundary layer moisture
ahead of the front will support at least weak instability and
thunderstorm potential. However, severe thunderstorm chances appear
low given richer boundary layer moisture will remain offset from
stronger shear/large-scale ascent.

Another upper shortwave trough is expected to move from the Rockies
into portions of the Plains late in the forecast period. As this
occurs, lee cyclogenesis is likely to occur, and southerly low-level
flow may transport modest Gulf moisture northward into the central
Plains to the MO Valley. Some increase in severe thunderstorm
potential could develop around Day 7 or 8/Wed or Thu, from the
southern/central Plains toward the MO Valley. However, confidence is
too low to include severe probabilities at this time given poor
run-to-run model consistency.

..Leitman.. 10/09/2025

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ACUS48 KWNS 100853
SWOD48
SPC AC 100851

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0351 AM CDT Fri Oct 10 2025

Valid 131200Z - 181200Z

...DISCUSSION...
...Monday/Day 4 to Wednesday/Day 6...
From Monday to Wednesday at mid-levels, a ridge is forecast to
remain over the central U.S., as a low moves into southern
California. Southwest flow is forecast over the Intermountain West
and Rockies. A chance for thunderstorms is expected to develop early
in the week ahead of the system, with a marginal severe threat
possible each afternoon across parts of Four Corners region. Any
severe threat should remain localized due to weak instability.

...Thursday/Day 7 and Friday/Day 8...
A shortwave trough is forecast to eject northeastward across the
central Rockies on Thursday, and into the northern Plains on Friday. Thunderstorms will be possible ahead of this trough, and in the
central Rockies Thursday afternoon. A severe threat could develop if
enough instability is realized ahead of the system. A secondary
trough is forecast to move across the Desert Southwest on Friday.
Isolated severe storms could occur ahead of this feature Friday
afternoon and evening, primarily in the southern Rockies. Although
this scenario on Thursday and Friday could pan out, the models
differ on the timing of the trough sequence. Also, instability is
forecast to be relatively weak. These factors suggest uncertainty,
and point to a more localized severe potential.

..Broyles.. 10/10/2025

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ACUS48 KWNS 110848
SWOD48
SPC AC 110846

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0346 AM CDT Sat Oct 11 2025

Valid 141200Z - 191200Z

...DISCUSSION...
....Tuesday/Day 4 to Thursday/Day 6...
On Tuesday and Wednesday, a mid-level low is forecast to move
northeastward across the Intermountain West, as an associated jet
streak translates across the Four Corners region. Thunderstorms will
be possible well to the east of the system, along and near an axis
of instability in the southern Rockies Tuesday afternoon and
evening, where a marginal severe threat could develop. Moisture
advection is forecast Tuesday night into Wednesday across the
central and northern Plains, where a pocket of moderate instability
could develop by Wednesday afternoon. Scattered thunderstorms will
be possible across parts of the central and northern High Plains
Wednesday afternoon and evening, near and to the east of the exit
region of the mid-level jet. An isolated severe threat could
materialize in areas where instability becomes the strongest.

On Wednesday, a secondary trough is forecast to move into the
Rockies, as southwest mid-level flow remains in place over the Great
Plains. Thunderstorms are expected to develop within this southwest
flow Thursday afternoon and evening over parts Nebraska and the
Dakotas, where a marginal severe threat will be possible.

...Friday/Day 7 and Saturday/Day 8...
The large-scale mid-level trough is forecast to move over the
Rockies on Friday, as a ridge moves eastward into the Ohio and
Tennessee Valleys. Thunderstorms will be possible Friday into Friday
night between these two features, along and ahead of a cold front
from the upper Mississippi Valley southwestward into the central
Plains. Convective coverage is expected to expand on Saturday across
the Mississippi Valley, as the exit region of a large-scale
mid-level jet moves across the region. A severe threat will be
possible along a corridor of maximized low-level moisture and
instability from the Ozarks northward into the mid to upper
Mississippi Valley. Concerning the potential for a severe weather
event on Saturday, uncertainty is substantial mainly due to the
extended range and wide variance among the model solutions.

..Broyles.. 10/11/2025

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ACUS48 KWNS 120900
SWOD48
SPC AC 120858

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0358 AM CDT Sun Oct 12 2025

Valid 151200Z - 201200Z

...DISCUSSION...
...Wednesday/Day 4 to Friday/Day 6...
A mid-level ridge is forecast to move slowly eastward from the
central and northern Plains on Wednesday to the Great Lakes and Ohio
Valley by Friday. During this time, a trough is forecast to move
eastward across the western half of the nation. Ahead of the trough
on Wednesday, isolated to scattered thunderstorms appear most likely
to develop from the southern Rockies into the northern Plains. An
isolated severe threat will be possible along and near the axis of
instability Wednesday afternoon and evening. The instability axis is
forecast to shift eastward into the central and northern Plains on
Thursday, and into the Upper Midwest on Friday. An isolated severe
threat will be possible along and near the instability axis on both
Thursday and Friday afternoon/evening.

...Saturday/Day 7 and Sunday/Day 8...
Low-level moisture advection is forecast to increase markedly on
Saturday as the trough moves into the Great Plains. By afternoon, an
axis of moderate instability could be in place from the southern
Plains into the Ozarks, with surface dewpoints in the 60s F.
Scattered to numerous thunderstorms may develop along and near this
axis of instability Saturday afternoon and evening. A severe threat
will be possible from Saturday into Saturday night as the trough
moves across the central U.S. A severe potential will also be
possible on Sunday, with the system forecast to move across the
Mississippi Valley.

Although there is model spread among the solutions, most have the
trough moving into the Great Plains on Saturday, with a moist and
unstable airmass located over the lower to mid Mississippi Valley.
This scenario seems plausible. However, the models do still have
significant variance on the timing and strength of the mid-level
system. For this reason, will not add a severe threat area at this
time.

..Broyles.. 10/12/2025

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ACUS48 KWNS 130900
SWOD48
SPC AC 130858

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0358 AM CDT Mon Oct 13 2025

Valid 161200Z - 211200Z

...DISCUSSION...
...Thursday/Day 4 to Saturday/Day 6...
On Thursday, a mid-level ridge is forecast to move eastward into the Mississippi Valley, as a low and an associated shortwave trough move northeastward into the northern Rockies and northern Plains.
Thunderstorm development is expected Thursday afternoon along and
ahead of a cold front from central Nebraska into the eastern
Dakotas. An isolated severe threat will be possible, but should be
marginal due to weak instability.

From Friday into Saturday, a large-scale mid-level trough is
forecast to move eastward from the central Rockies and Intermountain
West into the Great Plains. Scattered thunderstorms will be possible
Friday afternoon and evening ahead of the trough along and near an
axis of instability from Oklahoma northeastward into northwest
Missouri. Forecast instability and deep-layer shear appear
sufficient for an isolated severe threat.

Friday night, low-level moisture advection is forecast to markedly
increase as surface dewpoints in the lower to mid 60s F overspread
the Ark-La-Tex, Ozarks and mid Mississippi Valley. Moderate
instability is expected to develop early in the day on Saturday
across parts of the moist sector, where moderate to strong
deep-layer shear will be in place. Thunderstorms that form along and
near the axis of strongest instability should obtain a severe
threat. Supercells with severe wind gusts, hail and tornado
potential will be possible. The magnitude of the severe threat will
be greatest in areas that remain unaffected by morning thunderstorm
activity. The severe threat should spread eastward into the lower to
mid Mississippi Valley Saturday evening and into the overnight
period. Although lingering uncertainties exist, confidence in the
model solutions is great enough to add a 15 percent area over parts
of Ark-La-Tex, Ozarks and lower to mid Mississippi Valley.

...Sunday/Day 7 and Monday/Day 8...
The mid-level trough is forecast to move eastward across the lower
to mid Mississippi Valley on Sunday and to the mid Atlantic Seaboard
on Monday. Thunderstorms will be ongoing Sunday morning, ahead of a
cold front moving through the Ohio and Tennessee Valleys. New
convective development is expected during the day on Sunday ahead of
the front as surface temperatures warm. Thunderstorm development
should also occur on Monday ahead of the front. However, instability
is forecast to remain relatively weak across much of the moist
sector on Sunday and Monday, suggesting the severe threat in most
areas will remain relatively isolated.

..Broyles.. 10/13/2025

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ACUS48 KWNS 140859
SWOD48
SPC AC 140857

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0357 AM CDT Tue Oct 14 2025

Valid 171200Z - 221200Z

...DISCUSSION...
...Friday/Day 4 and Saturday/Day 5...
A large-scale mid-level trough, and an associated cold front are
forecast to move across the central U.S. on Friday and Saturday.
Isolated to scattered thunderstorms are expected to develop from
late Friday afternoon into the evening along and ahead of the front
from the southern Plains northeastward into the lower to mid
Missouri Valley. Ahead of much of the front, MLCAPE is forecast to
peak around 1000 J/kg with 0-6 km shear ranging from 30 to 40 knots.
This should be sufficient for an isolated severe threat. Cells with
potential for large hail and severe wind gusts will be possible.

On Saturday, moisture advection is forecast to markedly increase
ahead of the approaching trough, as surface dewpoints increase into
the 60s F over much of the moist sector. In spite of this,
instability will be tempered over parts of the Ozarks by ongoing
convection Saturday morning. The models suggest that an axis of
moderate instability will develop a bit further west by afternoon,
with MLCAPE increasing to the 1500 to 2000 J/kg range, mainly in the Ark-La-Tex. Thunderstorms that develop along and near the
instability axis should obtain a severe threat. Moderate deep-layer
shear is forecast over much of the moist sector, which will
contribute to a potential for supercells with wind damage, hail and
potentially a tornado threat. Storm mode is still uncertain, and
linear mode could become favored relatively early in the event.
Under this scenario, wind damage would be the most likely of the
three hazards. The severe threat should persist into the overnight
period, as an MCS moves eastward through the lower to mid
Mississippi Valley.

...Sunday/Day 6 to Tuesday/Day 8...
Widespread convection is expected to be ongoing Sunday morning
across the Ohio and Tennessee Valleys southward into the central
Gulf Coast states. This convection, along with abundant cloud cover,
should limit destabilization over much of the moist sector during
the day. In spite of this, an isolated severe threat could develop
in areas where sufficient surface heating takes place, from parts of
northern Florida northward into the southern Appalachians. The
severe threat is expected to diminish across the eastern U.S. on
Monday and Tuesday, as the cold front moves offshore into the
western Atlantic. However, uncertainty is still substantial at this
forecast range.

..Broyles.. 10/14/2025

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ACUS48 KWNS 150858
SWOD48
SPC AC 150857

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0357 AM CDT Wed Oct 15 2025

Valid 181200Z - 231200Z

...DISCUSSION...
...Saturday/Day 4...
A large-scale mid-level trough will move through the Great Plains on
Saturday, with a moist airmass in place across the Ark-La-Tex,
Ozarks and lower Mississippi Valley. Within this airmasss, an area
of thunderstorms is likely to be ongoing at the start of the period
across parts of eastern Oklahoma and southwest Missouri. Ahead of
this convection, moisture advection and surface heating will
contribute to a moderately unstable airmass by midday, with
forecasts increasing MLCAPE to around 1500 J/kg across the
Ark-La-Tex. Thunderstorm development appears likely in the early
afternoon over much of Ozarks, where moderate deep-layer shear is
forecast. The ECWMF is forecasting 0-6 km shear in the 40 to 50 knot
range over this part of the moist sector, suggesting a severe threat
will be probable during the afternoon. Wind damage will be possible
with bowing line segments, and low-level shear should be sufficient
for tornadoes. Hail will also be possible, mainly if supercells can
develop. Storm mode still remains uncertain. If the mode goes linear
early in the event, the wind-damage threat could become dominant.
The severe threat should persist through the evening and into the
overnight period, as an MCS moves through the central Gulf Coast
states.

...Sunday/Day 5 and Monday/Day 6...
The mid-level trough is forecast to move through the Ohio and
Tennessee Valleys on Sunday, and to the Atlantic Seaboard on Monday.
Ahead of the trough, scattered thunderstorms with an isolated severe
threat will be possible Sunday and Sunday night, with much of the
convection moving offshore into the Atlantic relatively early on
Monday. An isolated severe threat would still be possible closer to
the mid-level low in parts of the Mid-Atlantic Monday afternoon.

...Tuesday/Day 7 and Wednesday/Day 8...
From Tuesday into Wednesday, a mid-level low is forecast to move
across the southwestern U.S., reaching the southern Rockies by
Wednesday night. If the models are relatively close on the system
timing, an isolated severe threat could develop ahead of the system
Wednesday night across the southern Plains. However, uncertainty at
this range is substantial.

..Broyles.. 10/15/2025

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