Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Tue Oct 31 2023 08:23:16

ACUS48 KWNS 310823
SWOD48
SPC AC 310821

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0321 AM CDT Tue Oct 31 2023

Valid 031200Z - 081200Z

....DISCUSSION...
After trending more zonal, or least less amplified, late this week
through next weekend, the latest medium-range guidance suggests that
there may be substantive amplification within the westerlies across
the southern mid-latitude eastern Pacific through the Atlantic
Seaboard during the early portion of next week.  It appears that
this may include the evolution of a significant, progressive short
wave trough to the east of the Rockies, downstream of larger-scale
mid-level ridging building across the Pacific coast through Rockies
and adjacent Great Plains.

Initially digging across the central Great Plains by early next
Monday, significant surface cyclogenesis now appears possible across
the Ozark Plateau into lower Ohio Valley as the trough amplifies
east-southeastward across the middle and lower Mississippi Valley.
The cyclone may deepen further while redeveloping to the east of the
Allegheny Mountains through the northern Mid Atlantic coast on
Tuesday, with a trailing cold front surging across much of the
Southeast and Mid Atlantic.

Given this potential synoptic forcing, an associated risk for severe
thunderstorm development might not be completely negligible.
However, in the wake of the significant preceding cold intrusion,
guidance still suggests that surface ridging may be maintained
across much of the northwestern Gulf of Mexico and Gulf Coast region
into late Sunday or early Monday.  It appears that this may preclude
a substantive return flow of moisture prior to the onset of
cyclogenesis.  And modest to weak boundary-layer
moistening/deepening within the warm sector may remain problematic
with regard to destabilization as it evolves across the central
through eastern U.S.  At this time, severe probabilities still
appear less than 15 percent for next Monday-Tuesday, but it is
possible that this could change in later outlooks for this period.

...Kerr.. 10/31/2023

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