ACUS48 KWNS 280826
SWOD48
SPC AC 280825

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0325 AM CDT Sun Sep 28 2025

Valid 011200Z - 061200Z

...DISCUSSION...
Strong cyclogenesis within the westerlies near the Aleutians late
this week into next weekend may lead to the development of an
increasingly prominent blocking pattern over the eastern
mid-latitude Pacific into western North America. This may include
an evolving low near the California coast, to the southeast of
building mid/upper high over the northeastern Pacific by the end of
the period. In general, though, stronger westerlies are forecast to
remain confined to the northern mid-latitudes, with little potential
for substantive cyclogenesis to the lee of the Rockies, and moist
return flow off the Gulf Basin. This likely will maintain generally
low convective potential across the nation.

..Kerr.. 09/28/2025

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ACUS48 KWNS 290830
SWOD48
SPC AC 290828

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0328 AM CDT Mon Sep 29 2025

Valid 021200Z - 071200Z

...DISCUSSION...
Latest model output is not much different from prior runs concerning
the continuation of generally low convective potential across the
U.S. into and through the medium-range period. Guidance continues
to suggest that an increasingly amplified regime across the
mid-latitude eastern Pacific into western North America could lead
to the evolution of a prominent blocking pattern late this week into
next weekend. By early next week, this may include a building
mid-level high over the northeastern Pacific, near the British
Columbia/Pacific Northwest coast, flanked by a pair of evolving lows
at somewhat lower latitudes, including one over the U.S.
Intermountain West. Otherwise, the stronger westerlies may retreat
to somewhat higher latitudes, and mid/upper ridging may build in the
southern mid- to subtropical latitudes east of the Rockies and
Mexican Plateau. Significant surface cyclogenesis still appears
unlikely to the east of the U.S. Rockies, and low-level moisture
return off the Gulf Basin may be slow to develop.

..Kerr.. 09/29/2025

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ACUS48 KWNS 300823
SWOD48
SPC AC 300822

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0322 AM CDT Tue Sep 30 2025

Valid 031200Z - 081200Z

...DISCUSSION...
Late this work week through the weekend, medium-range models
continue to indicate mid/upper flow amplification across the
mid-latitude eastern Pacific into North America, which may lead to
the evolution of an increasingly prominent blocking high offshore of
the British Columbia/Pacific Northwest coast. This would probably
be flanked by persistent troughing at somewhat lower latitudes,
including California coastal areas into the Great Basin. However,
the spread within/among the model output is sizable concerning this
and subsequent developments through early next week.

Stronger and more progressive westerlies, and potential for
significant surface cyclogenesis, may remain confined to the higher
latitudes. However, there does appear a consensus within the
medium-range output of modestly deepening surface troughing across
parts of the central Great Plains into Upper Midwest (roughly along
an axis from the Front Range through Minnesota) by this weekend,
perhaps as one notable short wave perturbation accelerates
northeastward out of the Intermountain West. In the presence of
steep lower/mid-tropospheric lapse rates and strengthening flow,
this could provide a focus for strong thunderstorm development
Saturday and/or Sunday. However, due to the continuing lack of a
substantive moist return flow off the Gulf, the potential for
organized severe storms still appears low.

..Kerr.. 09/30/2025

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ACUS48 KWNS 010851
SWOD48
SPC AC 010850

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0350 AM CDT Wed Oct 01 2025

Valid 041200Z - 091200Z

...DISCUSSION...
Downstream of a building mid-level ridge, and perhaps evolving
embedded high over the northeastern Pacific, it appears that
large-scale troughing will be maintained across the Great
Basin/Southwest vicinity through this coming weekend and beyond.
However, an initially notable short wave trough, digging into the
Great Basin by late this week, is forecast to accelerate across and
northeast of the Rockies, through northern Ontario, Saturday into
early next Monday morning. The extent to which it maintains
strength as it eventually consolidates into mid-level troughing
shifting across and east of the Canadian Prairies, remains unclear.
But, latest medium-range output appears to be trending deeper with
developing surface troughing, and perhaps a relatively compact
evolving surface cyclone, northeast of the Front Range through the
northern Great Plains/Upper Midwest vicinity.

Preceded by a northeastward advecting plume of elevated mixed-layer
air, strengthening flow and shear could contribute to potential for
organized severe convection across parts of western/central Nebraska
through the eastern Dakotas/western Minnesota late Saturday into
Saturday evening, and perhaps farther east across the Upper
Midwest/adjacent Great Lakes vicinity on Sunday. However, this
threat still appears largely conditional. It will probably take
greater boundary-layer moistening than is currently suggested
possible by the medium-range output to support more than relatively
minor severe weather potential in the form of a few strong gusts, in
the presence of thermodynamic profiles characterized by a deeply
mixed boundary layer with sizable lower/mid-tropospheric dew point
spreads.

Into the early through middle portion of next week, the mid/upper
flow evolution becomes more unclear, but guidance continues to
indicate little potential for organized severe thunderstorms.

..Kerr.. 10/01/2025

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ACUS48 KWNS 020848
SWOD48
SPC AC 020847

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0347 AM CDT Thu Oct 02 2025

Valid 051200Z - 101200Z

...DISCUSSION...
Medium-range guidance indicates that blocking within the westerlies
across the mid-latitude eastern Pacific will remain prominent into
the middle to latter portion of next week. However, one mid-level
high forming off the Pacific coast this weekend may be relatively
short-lived, and subsequent developments off the Pacific into North
America remain unclear, based on rather large spread apparent in the
model output.

Early in the period, a still notable, but perhaps weakening,
mid-level short wave perturbation, and associated compact surface
cyclone, may quickly migrate from the eastern Dakotas through
northwestern Ontario during the day Sunday. In the presence of
seasonably strong and sheared lower/mid-tropospheric wind fields,
there appears at least some potential for renewed strong to severe
thunderstorm development, mainly across parts of north central
Minnesota through the western Lake Superior vicinity by Sunday
evening. However, mostly due to a continuing lack of better
low-level moisture return, potential for destabilization supportive
of more than a relatively isolated/marginal severe risk still seems
low or at least uncertain.

Elsewhere, there appears at least some signal for increasing
convective potential ahead of an amplifying short wave trough and
associated cold front advancing southeast of the lower Great Lakes
region, which could impact the Northeastern urban corridor by late
Wednesday. At this point, this appears most notable in ECMWF/ECENS
related output, compared to other model output, at a period of
increasing model spread and low predictability.

..Kerr.. 10/02/2025

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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 040840
SWOD48
SPC AC 040839

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0339 AM CDT Sat Oct 04 2025

Valid 071200Z - 121200Z

...DISCUSSION...
A cold front will move offshore the Northeast coast and develop
southward in the Mid-South/TN Valley area early the forecast period
(around days 4-5/Tue-Wed). Severe thunderstorm potential is expected
to be low as the front progresses given limited destabilization
across the warm sector.

The second half of the forecast period (days 6-8/Thu-Sat) becomes
more uncertain as spread among forecast guidance increases
considerably. Most guidance shows upper ridging building over the
Plains through much of the period. Toward the weekend, an upper
trough may develop southeast across the eastern half of the CONUS,
but details regarding timing and spatial evolution of this feature
vary considerably, resulting in low forecast confidence.

..Leitman.. 10/04/2025

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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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