Subj : DAY1SVR: Marginal Risk
To   : ALL
From : Mike Powell
Date : Wed Sep 20 2023 21:16:00

ACUS01 KWNS 210052
SWODY1
SPC AC 210051

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0751 PM CDT Wed Sep 20 2023

Valid 210100Z - 211200Z

....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE INTERMOUNTAIN WEST AND ARK-LA-TEX...

....SUMMARY...
A marginal severe threat will be possible this evening in parts of
the Intermountain West and in a small part of the Ark-La-Tex.

....Intermountain West...
Latest water vapor imagery has a mid-level low over northeastern
Oregon, with southwesterly flow located over much of the northern
Rockies and northern High Plains. At the surface, a cold front is
located in western Idaho, with a weakly unstable airmass ahead of
the front. Thunderstorms are ongoing along the western edge of the
stronger instability from northeast Nevada northeastward into
southeastern Idaho. RAP forecast soundings in southeast Idaho this
evening have weak instability, moderate deep-layer shear and low to
mid-level lapse rates exceeding 8 C/km. The steep lapse rates will
aid downdraft acceleration, and a few marginally severe gusts could
occur ahead of the faster moving cells this evening.

....Ark-La-Tex...
Latest water vapor imagery shows an mid-level ridge in the southern
High Plains, with west-northwesterly flow over much of the southern
Plains and Ark-La-Tex. At low-levels, a moist airmass is in place
over Oklahoma, Arkansas and east Texas. As a 30 to 40 knot low-level
jet strengthens this evening into tonight, isolated thunderstorms
are expected to develop over parts of the Ark-La-Tex. RAP forecast
soundings in far southeast Oklahoma at 06Z have MUCAPE near 1200
J/kg, effective shear around 40 knots, and 850-500 mb lapse rates
near 7 C/km. This could be enough for a marginal hail threat with
the strongest of cells.

...Broyles.. 09/21/2023

$$

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