Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Wed Nov 23 2022 08:47:25

ACUS48 KWNS 230847
SWOD48
SPC AC 230845

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0245 AM CST Wed Nov 23 2022

Valid 261200Z - 011200Z

....DISCUSSION...
A closed upper low is forecast to be over the southern Plains on Day
4/Sat, and lift northeast through Day 5/Sun, moving offshore the
Mid-Atlantic/New England coast by Sunday night. A weak surface low
will likewise shift northeast during this time, from OK into
southern Ontario. As this occurs, a cold front will shift east
across the Gulf Coast states on Saturday, before moving offshore
from the Mid-Atlantic/Carolinas/Georgia coasts on Sunday. Mid/upper
60s surface dewpoints will spread across the Southeast ahead of the
front, and a couple of strong storms may move across MS/AL on
Saturday. However, widespread cloudiness, and ongoing
showers/thunderstorms will likely limit inland destabilization while
stronger large-scale ascent shifts northeast of the region. As a
result, severe potential appears limited at this time.

By Day 6/Mon, medium range guidance has persistently shown another
large-scale upper trough developing over the western U.S. and
ejecting eastward toward the Plains on Day 7/Tue. Deterministic and
ensemble guidance is in greater than average agreement that severe
thunderstorm potential will develop ahead of the ejecting trough on
Tuesday across parts of OK/TX/AR/LA. The current expectation is that
surface cyclogenesis over the central/southern High Plains will
allow increasing southerly flow to transport rich Gulf moisture
northward across the Arklatex vicinity toward the Ozark Plateau. As
the trough ejects eastward, favorable vertical shear will overlap
deep boundary-layer moisture and sufficient instability to set the
stage for a potential severe weather episode late Tuesday afternoon
into early Wednesday morning. Given deterministic, ensemble and
machine learning guidance consistency, a 15 percent delineation has
been included. This area may shift with time depending on forecast
guidance trends over the next few days, but reasonable confidence
exists at this time that severe potential will develop over the
south-central U.S. vicinity on Tuesday.

Severe thunderstorm potential may continue toward the Lower MS
Valley/central Gulf Coast vicinity on Day 8/Wed as the upper trough
continues eastward along with an eastward-advancing cold front.
However, severe potential will be influenced by the evolution of
convection on Tuesday, and uncertainty is too great at this time to
delineate an area for Wednesday.

...Leitman.. 11/23/2022

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