ACUS48 KWNS 020902
SWOD48
SPC AC 020900

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0400 AM CDT Wed Apr 02 2025

Valid 051200Z - 101200Z

...DISCUSSION...
The mid-level flow pattern will undergo significant amplification
over the next several days as a large western US trough begins to
move eastward. Very rich moisture will support widespread
thunderstorm potential across parts of the Southeast and eastern US
through the weekend.

...D4/Saturday Mid South...
The upper low over northern Mexico will continue to amplify as it
begins ejecting eastward across the lower and mid MS Valley. A
strong 100+ kt jet will move east of the trough and overspread a
relatively broad warm sector across the Sabine and MS Valleys into
parts of TN/KY. Unseasonably rich moisture from several days of
southerly flow will be in place ahead of a surface low and cold
front. One or more rounds of severe storms, including supercells,
appears likely from eastern TX into AR, LA, and MS through the day.
All hazards will be possible. Storms should eventually grow upscale
into a line or cluster and spread eastward overnight into parts of
AL, FL, and GA.

The northern bound of the risk area across the TN Valley and into
the OH valley appears somewhat conditional. Multiple preceding days
of storms may limit the northern extent of the deeper moisture and
buoyancy. However, some severe risk likely exists given the
intensity of the low-level jet and abundance of moisture.

...Day 5...
The severe threat is likely to carry over from Day 4 in the form of
a squall line, as the upper wave gradually devolves into a broader positive-tilt trough. Strong mid-level flow and ascent will persist
over a broadening warm sector across the Southeast. While lapse
rates appear weak from several days of convection, some severe risk
is possible. The intensity of the severe risk will be heavily
dependent on the convective evolution from the prior day 4 which is
very unclear at the moment. Will add a 15% area across parts of AL,
FL, GA and SC where the best overlap of mid-level flow and robust
moisture are expected to support potential for damaging gusts.

A severe risk may also develop across parts of the Carolinas and mid
Atlantic Day5/Sunday. As the upper wave lifts to the north, ascent
will overspread returning surface moisture as far north as southern
PA. It is unclear how much buoyancy will be present with the
potential for widespread clouds. However, strong flow fields will be
available to any convection that can develop.

...D6+...
Offshore flow and high pressure will begin to dominate the extended
period as mid-level ridging intensifies over the center of the
country. Much cooler and stable conditions behind the advancing cold
front appear likely to temporarily end broader potential for severe
storms through early next week.

..Lyons.. 04/02/2025

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ACUS48 KWNS 120843
SWOD48
SPC AC 120841

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0341 AM CDT Sat Apr 12 2025

Valid 151200Z - 201200Z

...DISCUSSION...
After a relative lull in severe potential mid-week, latest guidance
indicates increasing severe possibilities late week. Compared to 24
hours ago, deterministic models have vastly changed to an evolution
of a shortwave trough digging south from the Canadian Rockies into
the Lower CO Valley during D5-7/Wednesday-Friday. This would support
a greater breadth and quality of western Gulf moisture advection
across the central states beneath an initially pronounced EML. SPC
and NSSL GEFS-based ML guidance indicate broadening 5 to mesoscale
pockets of 15 percent probabilities during D6-8/Thursday-Saturday.
But given the lack of day-to-day continuity and rather large spread
across ensemble guidance, consideration of any severe area appears
premature this cycle.

..Grams.. 04/12/2025

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ACUS48 KWNS 130853
SWOD48
SPC AC 130851

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0351 AM CDT Sun Apr 13 2025

Valid 161200Z - 211200Z

...DISCUSSION...
An active severe weather pattern is expected late week into next weekend.

...D5/Thursday...
Guidance has converged to a signal of severe-storm threat centered
on Thursday evening as a deep surface cyclone becomes established in
the KS vicinity, downstream of a longwave trough in the West. An
enriching low-level moisture plume will be advected nearly due north
from the western Gulf towards the Lower MO Valley. A stout EML
should limit convective development along much of the dryline. But a strengthening low-level jet should support thunderstorm development
to the northeast of the surface low amid strong deep-layer shear.

...D6/Friday...
A rather broad swath of 50+ kt 500-mb southwesterlies appears likely
to become established from the southern High Plains to the Great
Lakes, downstream of a broad trough in the Southwest and a separate northern-stream wave around northern ON. While the deep cyclone over
the KS vicinity will weaken, it should track towards the central
Great Lakes in response to the northern wave. Along its trailing
cold front, extensive thunderstorm development is anticipated Friday afternoon/evening. Given the aforementioned strong mid-level flow
regime, a broad corridor of severe threat is warranted.

...D7-8/Saturday-Sunday...
Predictability for a 15 percent highlight wanes somewhat next
weekend, but areas will probably be needed in later outlooks.
Saturday may consist of confined, bimodal threat areas across the
Lower Mid-Atlantic States and southern High/Great Plains. For the
former, the degree of instability and position of a southeast-moving
cold front on the periphery of a fast zonal flow regime are the main uncertainty drivers. For the latter, timing of the pivot and
eastward ejection of the Lower CO Valley shortwave impulse into the south-central states will be critical. Based on latest guidance, it
appears Sunday could have a broader corridor of severe potential.

..Grams.. 04/13/2025

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ACUS48 KWNS 140852
SWOD48
SPC AC 140850

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0350 AM CDT Mon Apr 14 2025

Valid 171200Z - 221200Z

...DISCUSSION...
Active severe weather pattern expected late week into the weekend.

...D4/Thursday...
A longwave trough should become clearly anchored over the West and
consist of multiple embedded shortwave impulses. Peak surface
cyclone amplitude is largely progged over western KS on Thursday
afternoon, with a dryline arcing across eastern KS into the southern
Great Plains. Another day of modifying moisture return northward
from the western Gulf should yield at least moderate buoyancy ahead
of the dryline. A strengthening low-level jet should support
thunderstorm development across the Lower MO to Mid-MS Valleys on
Thursday evening. Supercell wind profiles support potentially
scattered severe storms.

...D5/Friday...
A broad swath of strong mid-level southwesterlies appears likely
to become established from the southern High Plains to the Great
Lakes, downstream of a longwave trough from James Bay to the Lower
CO Valley. While the deep cyclone over the KS vicinity will weaken,
it should move towards the central Great Lakes. From along/ahead of
its track to the trailing cold front arcing southwestward into west
TX, extensive thunderstorm development is anticipated Friday
afternoon/evening. Given the strong mid-level flow regime, scattered
severe storms are possible across an elongated corridor.

...D6-7/Saturday-Sunday...
Predictability for a 15 percent highlight remains too low during the
weekend, but areas will probably be needed in later outlooks.
Guidance has trended neutral to slightly weaker/more confined
potential on Saturday. Overall signal persists of bimodal primary
threat areas across the Lower Mid-Atlantic States and southern
High/Great Plains. For the former, the degree of instability and
position of a southeast-moving cold front on the periphery of
stronger zonal mid-level flow remain key uncertainty factors. For
the latter, timing of the pivot and eastward ejection of the compact
Lower CO Valley shortwave impulse across the Southwest/southern
Rockies remains crucial. Guidance has shown poor run-to-run
continuity for Sunday, yielding low confidence on spatial details of
the severe threat. Across both regimes and days, NSSL GEFS ML sub-15
percent probabilities appear quite reasonable.

..Grams.. 04/14/2025

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ACUS48 KWNS 150900
SWOD48
SPC AC 150858

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0358 AM CDT Tue Apr 15 2025

Valid 181200Z - 231200Z

...DISCUSSION...
An active severe weather pattern expected through at least this
weekend, before predictability diminishes early next week.

...D4/Friday...
Guidance remains consistent with a broad swath of strong mid-level southwesterlies from the southern High Plains to the Great Lakes,
downstream of a longwave trough from northern ON to the Lower CO
Valley. This will overlap a similarly oriented surface front. In
response to increasing mid-level height falls, a surface cyclone
should track across the central Great Lakes portion of the
baroclinic zone during the day. Afternoon severe may be focused in
this region with stronger low-level shear. Parts of this region may
warrant higher probabilities in later outlooks.

Farther southwest, a pronounced EML may delay the bulk of storm
development along the front until evening. But given the strong
deep-layer shear and moderate buoyancy, scattered severe storms
appear possible.

...D5/Saturday...
Amplification of an embedded northern-stream shortwave impulse over
ON/QC should sustain an expansive swath of strong mid-level flow
from the OH Valley northeastward. The northeast extent of
appreciable instability overlapping with this regime becomes
nebulous east of the Appalachians, but scattered severe storms seem
possible from the Cumberland Plateau into the Mid-South on Saturday
afternoon to evening.

Over the southern Great Plains, lingering convection Saturday
morning renders uncertainty along the largely stalling baroclinic
zone that will undoubtedly be modified by convective outflow. But
with greater consistency in guidance handling the pivot of the basal
shortwave impulse across the Southwest, multiple rounds of strong to
severe convection are plausible through Saturday night.

...D6/Sunday...
Predictability lessens by this period with the evolution of compact
shortwave trough ejecting onto the southern Great Plains. This
yields substantial spread in the attendant synoptic cyclone. In
addition, potentially extensive ongoing convection Sunday morning
further lessens confidence in mesoscale details. But a belt of
potentially very strong mid-level southwesterlies overlapping rich
western Gulf moisture supports inclusion of a severe-area highlight
in the South-Central States.

..Grams.. 04/15/2025

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ACUS48 KWNS 170831
SWOD48
SPC AC 170830

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0330 AM CDT Thu Apr 17 2025

Valid 201200Z - 251200Z

...DISCUSSION...
...Day 4/Sun - ArkLaTex to the Mid-MS Valley...

A compact upper shortwave trough is forecast to move from the
southern High Plains to the Midwest on Sunday. While some forecast
uncertainty continues with regard to exact position of this feature,
the overall pattern suggests isolated to scattered severe
thunderstorm potential will exist across portions of east TX into
the Mid/Lower MS Valley.

Strong southwesterly flow aloft will overspread a moist warm sector
as a surface low lifts north/northeast from OK into the Lower MO
Valley through early evening. A trailing cold front will spread east
as this occurs, while a warm front extends eastward from the Mid-MS
Valley into the OH Valley. Evolution of prior days convection is
resulting in some uncertainty regarding the western/northern extent
of severe potential. Nevertheless, a favorable environment
supporting at least isolated severe storms should extend from east
TX into parts of southern MO/IL ahead of the cold front.

...Days 5-8/Mon-Thu...

Forecast ensemble guidance from both the GEFS and EPS suggest
low-amplitude west/southwesterly flow will overspread the southern
tier of the U.S. next week. Southerly low-level flow on Day 5/Mon
across the western Gulf into the southern Plains in the wake of the
cold frontal passage on Day 4/Sun will allow for northward transport
of modified moisture. This should continue into Day 6/Tue across the
Plains. Some localized severe risk could develop across parts of the
southern Plains as an upper shortwave trough moves across the
north-central U.S. on Day 6/Tue, but poor juxtaposition between
higher quality moisture across OK/TX and stronger forcing across the
northern Plains/Upper Midwest may limit overall potential. This
low-amplitude pattern will continue through Day 8, resulting in low predictability.

..Leitman.. 04/17/2025

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ACUS48 KWNS 250856
SWOD48
SPC AC 250854

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0354 AM CDT Fri Apr 25 2025

Valid 281200Z - 031200Z

...DISCUSSION...
...Day 4/Mon - Southern Plains to Upper Midwest...

A strong mid-level jet streak will move rapidly northeastward from
the Southwest to the Upper Midwest on Monday. As this occurs, a
surface low will deepen and move from the northern Plains to the
northern Great Lakes. Strong southwesterly lower tropospheric flow
will advect high theta-e air northward across the Midwest and into
parts of the Upper Midwest. Broken to scattered cloudcover will
support surface heating and strong destabilization across the warm
sector from southeast Minnesota and western Wisconsin to the
southern Plains. Isolated to scattered supercells are likely along
the dryline which will extend from the southern Plains and into Kansas.

The greatest focus for severe weather on Monday will be from eastern
Kansas into northern Missouri, much of Iowa and into southern
Minnesota and western Wisconsin. Moderate to strong instability,
strong shear, and increasing forcing for ascent supports the
potential for numerous rounds of severe thunderstorms. The wind
profile supports supercells capable of all severe weather hazards
including the potential for strong tornadoes.

...Day 5/Tue - Southern Plains to parts of the Northeast...

The surface low associated with the Day 4 threat will continue
northeast and bring its associated cold front eastward across the
Midwest and Great Lakes through the day Tuesday. Moderate to strong
instability is forecast south of this front from northern New York
to the Ohio Valley. Much of the frontal zone should have sufficient
shear to support multiple storm clusters and the potential for a few supercells.

Day 6/Wed-Day8/Fri - Portions of the Mid-Mississippi Valley into the Southeast...

A weaker mid-level shortwave trough is consistently depicted by
extended range guidance by the middle of next week across the
southern Plains. However, significant uncertainty remains about the
strength of this trough and location of any frontal zones. In
addition, convection across the southern Plains each day of the
extended range forecast could significantly impact destabilization
by Day 6-8. Therefore, confidence is not high enough to add
probabilities at this time, but they may eventually be needed
somewhere across the Southeast/Mid Mississippi Valley.

..Bentley.. 04/25/2025

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ACUS48 KWNS 260849
SWOD48
SPC AC 260848

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0348 AM CDT Sat Apr 26 2025

Valid 291200Z - 041200Z

...DISCUSSION...
...Day 4/Tuesday - West Texas to the Northeast...
Moderate instability will be present along an elongated frontal zone
from the southern Plains to the Northeast on Tuesday. Modest shear
along the frontal zone will support some organization into multicell
clusters and perhaps supercells. A greater severe weather threat
will exist across the eastern Great Lakes where forcing and shear
will be strongest as a 75 knot mid-level jet streak crosses southern
Ontario.

Another focused zone of greater coverage of severe storms will be
across parts of West Texas where multiple rounds of storm are
anticipated. The first chance of storms will be during the afternoon
as the front continues to move south across Oklahoma and perhaps
into North Texas. An additional round of storms will be possible
across parts of West Texas as the low-level jet strengthens Tuesday
night in the presence of strong instability and shear.

...Day 5/Wednesday - North Texas to the ArkLaTex...
Ongoing Day 4 convection may have some impact on the exact location
of the severe weather threat on Tuesday. However, regardless of Day
4 convective evolution, there will likely be a region with a more
focused severe weather threat on Day 5/Wednesday where moderate to
strong instability exists ahead of strengthening mid-level flow and
a mid-level trough which will move across the southern Plains. 15% probabilities have been added for Day 5 from North Texas to the
ArkLaTex where this location of greatest severe weather threat
appears most likely at this time.

..Bentley.. 04/26/2025

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