ACUS01 KWNS 221242
SWODY1
SPC AC 221240

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0740 AM CDT Mon Sep 22 2025

Valid 221300Z - 231200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN/CENTRAL PLAINS...LOWER/MID MISSOURI VALLEY...AND OHIO VALLEY...

...SUMMARY...
Scattered severe thunderstorms will be possible this afternoon into
tonight across portions of the southern/central Plains, lower/mid
Missouri Valley, and Ohio Valley. Large hail and severe/damaging
winds should be the main threats.

...Synopsis...
Weak upper troughing over the Upper Midwest is forecast to drift
slowly eastward today across the upper Great Lakes, while upper
ridging remains centered over Mexico and south TX. In between these
two features, a broad zone of modestly enhanced west-northwesterly
mid-level flow will persist through the period. Multiple
low-amplitude mid-level perturbations should aid convective
development today and tonight across portions of the
southern/central Plains into the mid MO Valley and Upper Midwest,
and across parts of the TN/OH Valleys into the lower Great Lakes.

...Southern/Central Plains...
With a stout cap in place (reference 12Z DDC observed sounding) and
weak large-scale ascent anticipated through much of the afternoon,
robust thunderstorm development across the southern/central Plains
will likely be delayed until early evening as a southerly low-level
jet strengthens. Modest low-level moist advection will occur to the
east of a weak lee trough and surface low over the central High
Plains this afternoon, with generally mid 60s to low 70s dewpoints
forecast across much of KS/OK. Diurnal heating of this moist airmass
will support a corridor of moderate to locally strong instability
extending from western KS southeastward into OK.

It still appears probable that ascent associated with a southerly
low-level jet will be needed to overcome the cap this evening, with
most high-resolution guidance suggesting thunderstorm initiation
occurring around 00-02Z or later. Even though westerly mid-level
winds are not expected to be overly strong, sufficient deep-layer
shear will be present to support organized updrafts. Current
expectations are for initial development to pose some hail threat,
with a couple of supercells possible. With time, scattered
severe/damaging winds should become the main risk as convection
grows upscale into a bowing cluster across western/south-central KS.
This severe threat may continue overnight into parts of
western/northern OK, with enhanced low-level shear potentially
supporting a brief embedded tornado. The southern extent of the
Marginal/Slight Risks across the southern Plains have been trimmed
based on latest guidance trends.

...Lower/Mid Missouri Valley into the Upper Midwest...
Thunderstorms ongoing this morning across far southeast MN into
western WI remained sub-severe overnight. Still, they may pose an
isolated hail/wind risk through the morning as they move eastward
across WI amid a destabilizing airmass. Overall confidence in the
development and evolution of convection from eastern NE into the
Upper Midwest today remains fairly low, as stronger ascent aloft
associated with the upper trough over the upper Great Lakes will
tend to remain displaced to the north of the surface warm sector.
Even so, additional convection should form along a front in northern
IA this afternoon/evening. With cool temperatures aloft and modestly
steepened mid-level lapse rates, this activity could pose a threat
for mainly severe hail given gradually strengthening westerly winds
with height through mid/upper levels. Other thunderstorms may form
late this afternoon or early evening across eastern NE and vicinity.
Greater instability should be present across this region compared to
locations farther north, along with enough deep-layer shear to
support some updraft organization. An initial hail threat with this
activity should transition to more of a wind risk with time this
evening as clustering occurs.

...Tennessee/Ohio Valleys to the Lower Great Lakes...
A shortwave trough associated with ongoing convection over the
Mid-South/lower OH Valley this morning will translate northeastward
today across much of the OH Valley. Modestly enhanced southwesterly
low/mid-level winds will exist this afternoon over this region, with
20-30 kt of deep-layer shear supporting mainly loosely organized
multicells. Multiple clusters should develop and gradually
strengthen through the afternoon as they spread northeastward across
a weakly unstable airmass. Even though poor lapse rates aloft are
expected, somewhat steepened low-level lapse rates via filtered
daytime heating should still promote some risk for isolated to
scattered damaging winds with these clusters. Most guidance shows a
greater concentration of strong convection across parts of
central/eastern KY into OH and western WV this afternoon/early
evening, in close proximity to the mid-level shortwave trough. A
Slight Risk has been included across this area given increased
confidence in a corridor of scattered damaging wind potential.

...Far Eastern Arizona into New Mexico...
Moisture remains limited this morning across eastern AZ and much of
southern/central NM, with surface dewpoints generally ranging from
the 40s to mid 50s. Westerly mid/upper-level flow across this region
is expected to gradually strengthen through the day as an upper
trough/low digs southward from the northern Rockies across the Great
Basin and towards the Four Corners region by late tonight. A weak
perturbation embedded within the mid-level westerly flow may aid
initial convective development this afternoon across the higher
terrain of east-central AZ and vicinity. This activity will spread
eastward across much of central NM through the remainder of the
afternoon and into the evening. While instability will likely remain
weak owing to limited low-level moisture, steepened low-level lapse
rates with daytime heating and moderate to strong deep-layer shear
should promote outflow-dominant convection with an isolated threat
for strong to severe wind gusts.

..Gleason/Grams.. 09/22/2025

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