Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Wed Apr 12 2023 09:02:30

ACUS48 KWNS 120902
SWOD48
SPC AC 120900

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0400 AM CDT Wed Apr 12 2023

Valid 151200Z - 201200Z

....DISCUSSION...
A extensive cold front is forecast to stretch from northwest WI
southwestward into the TX Hill Country early D4/Saturday.
Medium-range guidance suggests mid 50s dewpoints will extend into
southern WI ahead of this front, with low 60s dewpoints reaching
into southern IL and mid 60s dewpoints reaching the Mid-South. Steep
mid-level lapse rates (i.e. about 7 deg C per km from 700 to 500 mb)
will likely cover much of the Mid MS Valley and Mid-South. These
lapse rates coupled with mid-60s dewpoints will result in moderate
to strong buoyancy ahead of the front. Vertical shear is not
expected to be overly strong, but should still support severe
storms. Discrete severe storms ahead of the main cold front appear
possible, with additional storms likely along the front itself. The
best overlap of forcing, shear, and buoyancy is anticipated from the
Mid-South into the Lower OH Valley, where a 15% outlook area was
delineated.

Thunderstorms are possible over the Upper OH Valley and Mid-Atlantic
along this front on D5/Sunday as it continues eastward. Low 60s
dewpoints may reach as far north as southern PA ahead of the front.
A negatively tilted shortwave trough may be moving into the northern
Mid-Atlantic as this time as well. Even with these favorable
dynamics and moderate low-level moisture, instability is still in
question given the poor lapse rates and likely limited heating.
These factors limit the predictability at this forecast range.

Given the moisture scouring from the previous frontal passage, the
severe potential appears low on D6/Monday. Low-level moisture may
begin returning on D7/Tuesday ahead of a low-latitude shortwave
trough, suggesting some severe potential may materialize early next
week.

...Mosier.. 04/12/2023

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