Subj : DAY3SVR: Nws Storm Prediction Center Norman Ok
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Mon Aug 21 2023 07:00:38

ACUS03 KWNS 210700
SWODY3
SPC AC 210659

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0159 AM CDT Mon Aug 21 2023

Valid 231200Z - 241200Z

....NO SEVERE THUNDERSTORM AREAS FORECAST...

....SUMMARY...
The risk for severe thunderstorms appears negligible across the
U.S., Wednesday through Wednesday night.

....Discussion...
It appears that the prominent warm-core ridging, encompassing much
of the nation east of the Rockies, may undergo further suppression
through this period, with the center of highest mid-level heights
shifting from the lower Missouri Valley toward the southern Great
Plains.  The more appreciable mid-level height falls are forecast to
be focused on the northern periphery of the ridge, where at least a
couple of short wave perturbations will progress through the
westerly flow.  However, it appears that the more prominent of these
will migrate north of the international border into the southern
Canadian Prairies, with broadly anticyclonic flow being maintained
across the downstream northern tier of the U.S. into the lee of the
lower Great Lakes region.

In association with digging mid-level troughing offshore of the
Atlantic Seaboard, a cold front may continue nosing southward to the
lee of the southern Appalachians.  At the same time, an area of weak
low pressure may develop eastward along a stalled segment of the
front that initially advanced south of the international border,
from the mid Missouri Valley into the Great Lakes region.

In advance of the frontal wave, seasonably moist air (supportive of
large mixed-layer CAPE beneath warm elevated mixed-layer air) may
advect across the Upper Midwest into the Great Lakes region
Wednesday through Wednesday night.  However, in the wake of
weakening early period warm advection driven convection across parts
of lower Michigan, the extent and potential of any renewed
thunderstorm development remains unclear.  Sustained thunderstorm
development rooted in the unstable boundary layer may remain
suppressed by inhibition associated with warm and dry layers aloft,
and the lack of mid/upper support for thunderstorm initiation. A
zone of strengthening lower/mid-tropospheric warm advection may
support another round of strong thunderstorm development Wednesday
night, but this may be focused mostly over southern Ontario.

...Kerr.. 08/21/2023

$$

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