325
ACUS01 KWNS 160554
SWODY1
SPC AC 160553

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1253 AM CDT Wed Sep 16 2026

Valid 161200Z - 171200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER NORTHERN
UTAH AND EASTERN PARTS OF THE OHIO VALLEY...

...SUMMARY...
A couple of strong to severe thunderstorms appear possible across
northern Utah and eastern parts of the Ohio Valley today.

...Synopsis...
A mid-level anticyclone will prevail over the southern Plains to the
TN Valley as a stationary upper trough morphs into a cut-off upper
low along the West Coast today. Multiple mid-level impulses will
pivot around the anticyclone and overspread the Midwest to OH
Valley, supporting occasional rounds of showers and thunderstorms.
Given rich low-level moisture along the northern periphery of the
mid-level anticyclone, a couple of strong to severe storms may
occur. A few strong to severe storms may also occur over portions of
northern UT as a pronounced mid-level impulse rotates around the
developing West Coast upper low, resulting in overlapping cooler
temperatures and stronger flow aloft.

...Northern UT...
As the aforementioned impulse pivots around the evolving upper low,
a 50+ kt 500 mb jet streak and corresponding 7 C/km mid-level lapse
rates will overspread northern UT during the day. Surface heating
will be limited given widespread cloud cover. Nonetheless, forecast
soundings suggest that surface temperatures near 70 F may yield
MLCAPE as high as 1500 J/kg given steep tropospheric lapse rates.
Furthermore, stronger winds aloft that gradually veer with height
will yield around 50 kts of effective bulk shear and elongated
hodographs with some low-level curvature. Multicells and perhaps
embedded supercells should be the primary storm mode, capable of
isolated instances of severe wind and/or hail.

...Midwest into the OH Valley...
Multiple rounds of showers and thunderstorms will be ongoing at the
start of the period (12Z Wednesday) and will continue through the
period (to 12Z Thursday). Some intensification of storms may occur
over OH and immediate surrounding areas with one weak impulse by
afternoon peak heating. Assuming some appreciable insolation can
occur, surface temperatures may rise through the 80s F, amid 70s F
dewpoints, contributing to 1500-2500 J/kg MLCAPE. Given meager
vertical wind shear, mainly pulse cellular and multicellular storms
are expected. The stronger storm cores may produce wet downbursts,
accompanied by an isolated damaging gust threat.

Another mid-level impulse will traverse the Midwest overnight, with
several CAM guidance members supporting nocturnal convective
initiation over IA in the 03-12Z period. At the moment, the
evolution of this convection is uncertain, so no severe
probabilities have been added. However, should more established
convection develop overnight, an instance of marginally severe hail
cannot be completely ruled out.

..Squitieri/Supinie.. 09/16/2026

$$