Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0206 AM CDT Fri Sep 18 2026

Valid 201200Z - 211200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE
CENTRAL HIGH PLAINS...SOUTHERN PLAINS...AND MIDWEST TO THE OHIO
VALLEY...

...SUMMARY...
Isolated severe thunderstorms, accompanied by mainly a wind and hail
threat, are possible across portions of the central High Plains, the
southern Plains, and the Midwest to Ohio Valley on Sunday.

...Synopsis...
A relatively zonal upper-air pattern will become established across
the CONUS on Sunday, with a mid-level low-amplitude shortwave trough
expected to eject into the central Plains while a more amplified
upper trough impinges on the California Coastline. As the Plains
low-amplitude upper trough progresses eastward, a surface cold front
will continue to sag southward across the southern Plains to the TN
Valley region. Thunderstorms should develop along or ahead of the
cold front. Relatively rich low-level moisture preceding the front,
along with modestly cooler temperatures aloft, may yield enough
buoyancy to support an isolated severe threat, mainly across the
southern Plains and the Midwest to OH Valley.

...Southern Plains...
Isolated to widely scattered thunderstorm initiation should take
place ahead of the surface cold front by afternoon peak heating,
especially over northern to central OK. Here, surface temperatures
climbing through the 80s F, amid upper 60s F dewpoints, will support
1000-2000 J/kg MLCAPE. Up to 40 kts of effective bulk shear, amid 7
C/km mid-level lapse rates, may encourage multicellular
organization, accompanied by mainly a severe wind/hail threat. Given
modest forcing for ascent, storm coverage is uncertain, so the
severe threat is currently anticipated to remain isolated.

...Central High Plains...
Upslope flow along the central High Plains will encourage enough
orographic lift for the development of a few thunderstorms by late
Sunday afternoon or evening. 7.5 C/km mid-level lapse rates and
elongated, straight hodographs with 50 kts of effective bulk shear
will favor stronger updrafts to organize into supercells. Severe
hail and wind will be the main threats.

...Midwest to OH Valley...
Surface dewpoints over 70 F will precede the cold front over the
Midwest to OH Valley corridor as it progresses southward. Both
pre-frontal and ana-frontal storm development is possible Sunday
afternoon. Over 2000 J/kg MLCAPE will exist ahead of the front,
though vertical wind shear should be modest (i.e. 25-35 kts of
effective bulk shear). A mix of multicells, short line segments, and
perhaps a supercell are likely. However, the severe threat is
currently anticipated to be relatively isolated in nature, with
mainly a few instances of severe wind or hail likely.

..Squitieri.. 09/18/2026

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0320 AM CDT Fri Sep 18 2026

Valid 211200Z - 261200Z

...DISCUSSION...
Initially zonal mid-level flow, with embedded low-amplitude impulses
traversing the central CONUS early next week, will give way to
gradual amplification of an upper ridge over the central U.S. The
best chance for any severe thunderstorms will be on Day 4/Monday
across the TN Valley, where a surface cold front, preceded by rich
low-level moisture, will be slow to clear the region. Thereafter,
drier low-level conditions will prevail across much of the central
and eastern CONUS, with surface high pressure poised to settle over
much of the U.S. between the MS River and the Appalachians, limiting
the severe threat.