Subj : DAY3SVR: Nws Storm Prediction Center Norman Ok
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Tue Aug 22 2023 06:57:13

ACUS03 KWNS 220657
SWODY3
SPC AC 220655

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0155 AM CDT Tue Aug 22 2023

Valid 241200Z - 251200Z

....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THURSDAY ACROSS
PARTS OF WESTERN PENNSYLVANIA AND ADJACENT SOUTHWESTERN NEW
YORK...WESTERN MARYLAND...MUCH OF WEST VIRGINIA...PARTS OF
NORTHEASTERN KENTUCKY...OHIO...SOUTHERN MICHIGAN...NORTHERN AND
CENTRAL INDIANA...NORTHERN ILLINOIS...PARTS OF SOUTHERN WISCONSIN
AND EASTERN IOWA...

....SUMMARY...
Strong thunderstorms may impact southern portions of the Great Lakes
region into the Ohio Valley Thursday afternoon and evening, posing
at least some risk for potentially damaging wind gusts.

....Synopsis...
While a significant mid-level short wave trough turns east of Hudson
Bay within the stronger westerlies, and a weaker impulse more slowly
begins to dig east-southeast of the Canadian Prairies into the
central international border vicinity, models indicate only a
continued gradual suppression of the persistent interior U.S.
ridging, across the northern Great Plains into the Mid Atlantic
region.  A prominent mid-level height center appears likely to be
maintained through this period across the central and southern Great
Plains into lower Mississippi Valley, as large-scale mid-level
troughing begins to consolidate near and offshore of the Pacific
Coast.

....Southern Great Lakes into Ohio Valley...
A notable cold front is forecast to progress southeast and south of
the Great Lakes region and Upper Midwest Thursday through Thursday
night, beneath lingering warm mid-level air along the northeastern
periphery of the ridging and, increasingly, south of the stronger
westerlies.  However, high pre-frontal boundary-layer moisture
content (including lower/mid 70s F surface dew points) and strong
daytime heating (well into the 90s F) probably will contribute to
large CAPE, beneath steep lower/mid-tropospheric lapse rates
associated with a plume of elevated mixed-layer air.

While mid/upper support for sustained thunderstorm development
remains unclear, it appears that there may be sufficient weakening
of inhibition to allow for the initiation of at least scattered
thunderstorm activity within the pre-frontal instability axis by
late Thursday afternoon.  Given the thermodynamic profiles, locally
damaging downbursts will be possible, and 20-30 kt westerly flow in
the 850-700 mb layer might be sufficient to support the evolution of
a few loosely organized clusters and cold pools posing a risk for
potentially damaging wind gusts.

...Kerr.. 08/22/2023

$$

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