Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0100 AM CDT Sun Sep 21 2025
Valid 211200Z - 221200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE
SOUTHERN PLAINS INTO THE OZARKS...MID MS VALLEY...OH VALLEY...AND
SOUTHERN GREAT LAKES...AND ALSO FROM NORTHEAST NE/SOUTHEAST SD INTO
SOUTHERN MN/NORTHERN IA...
...SUMMARY...
Isolated severe thunderstorms are possible later today across parts
of the southern Plains into the Ozarks, mid Mississippi Valley, Ohio
Valley, and southern Great Lakes. A few strong to severe
thunderstorms are also possible from the mid Missouri Valley into
southern Minnesota and northern Iowa.
...Synopsis...
A broad mid/upper-level trough will cover much of the
central/eastern CONUS later today, with several embedded vorticity
maxima expected to move across parts of the Great Plains into the
Midwest and Ohio Valley. Modest midlevel flow atop a sufficiently
moist and unstable environment will support some potential for
strong to locally severe storms across a relatively large area.
Localized corridors of somewhat greater severe threat may evolve
where deep-layer shear is enhanced by one of the embedded midlevel
shortwaves, as well as where midlevel flow veers to
west-northwesterly across parts of the mid MO Valley and southern
Plains.
...Parts of TX into southern OK...
Extensive overnight convection is expected to leave a residual
outflow boundary that will be located somewhere in the vicinity of
north TX/southern OK by afternoon. While some midlevel warming is
expected across the southern Plains through the day, relatively
strong heating, and the potential influence of an MCV that may
evolve from overnight convection, will support isolated to widely
scattered storm development this afternoon/evening near the outflow
boundary, and potentially southward along a diffuse dryline into
northwest/west-central TX.
Moderate buoyancy and 35-50 kt of effective shear within the
northwesterly flow regime across parts of north TX into southern OK
will conditionally support splitting supercells capable of producing
hail and localized severe gusts. There is some uncertainty regarding
the placement of the boundary by afternoon and the magnitude of any
MCV-related enhancement to deep-layer shear and storm coverage, but
greater probabilities may be needed if confidence increases in
development of multiple supercells and/or an organized cluster
within this regime.
...Northeast NE/southeast SD into southern MN/northern IA...
A compact mid/upper-level low will move southeastward from eastern
ND into MN later today. This low and the attendant shortwave trough
will aid in the development of isolated to widely scattered storms
by late afternoon or early evening from southwest MN into adjacent
southeast SD, northeast NE, and northwest IA, in the vicinity of a
weak surface boundary. Relatively cool temperatures aloft, moderate
buoyancy, and effective shear of 25-35 kt will support strong
multicells and perhaps a couple splitting supercells. Large hail is
expected to the primary hazard, though localized strong gusts will
also be possible with the strongest storms.
...Eastern KS into MO...
A cluster of elevated convection will likely be ongoing at the start
of the period across central/eastern KS. This cluster and possibly
an attendant MCV may encounter an environment across parts of MO
that is recovering from a separate area of overnight convection near
the Ozarks. While background midlevel flow will only support
effective shear of 20-25 kt, any MCV-related enhancement to the flow
would result in sufficient deep-layer shear for somewhat more
organized storms. If sufficient destabilization can occur, then a
few modestly organized cells or clusters may evolve this afternoon
and evening, accompanied by a threat for localized damaging wind and
perhaps some hail.
...Parts of the Ohio Valley and Great Lakes...
Modest deep-layer southwesterly flow will overspread parts of the
southern Great Lakes and Ohio Valley later today, in advance of the
midlevel shortwave trough moving across the upper MS Valley.
Scattered thunderstorm development is expected across the region,
within a moderately unstable and weakly capped environment. Midlevel
lapse rates and deep-layer shear are expected to remain relatively
weak, but steepening low-level lapse rates will result in potential
for cells/clusters capable of locally damaging wind this afternoon
into the early evening. There is also some potential for a storm
cluster or loosely organized MCS to develop across the lower MO/mid
MS Valley and move toward parts of the southern Great Lakes later
tonight.
..Dean/Halbert.. 09/21/2025
Read more CHECK UPDATE ZOOM GRAPHIC
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