Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Thu Dec 12 2024 09:21:51

ACUS48 KWNS 120921
SWOD48
SPC AC 120920

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0320 AM CST Thu Dec 12 2024

Valid 151200Z - 201200Z

....DISCUSSION...
Most of the medium-range guidance has trend faster and less
amplified with the shortwave trough expected to move from the Four
Corners region through the central Plains on D4/Sunday. This more
northerly progression will limit the interaction between this wave
and any returning low-level moisture, which should limit
thunderstorm potential throughout most of the day.

Another shortwave trough is expected to follow in the wake of this
lead wave, but with a more southerly track across the Southwest and
into the southern Plains. Guidance is in relatively good agreement
that this wave will move over the southern High Plains late
D4/Sunday into early D5/Monday. This wave is expected to interact
with the returning low-level moisture, with thunderstorm development
along and ahead of its associated front from central OK/north TX
into the Ozarks early Monday morning. Thunderstorms are expected to
gradually shift eastward throughout the day D5/Monday, expanding
into more of east/southeast TX and the Mid/Lower MS Valley.
Seasonally warm and moist conditions are anticipated, and enough
buoyancy and shear could be in place for severe thunderstorms.
However, overall buoyancy will likely be mitigated by poor lapse
rates, and warm mid-level temperatures could contribute to some
inhibition. There is also some potential for a more front-parallel
orientation, which could result in a more anafrontal character to
the storms. These factors, combined with the notable variability
within the guidance, introduce enough uncertainty to merit
withholding any severe probabilities for D4/Sunday or D5/Monday with
this outlook.

Another shortwave trough may progress into the Plains on
D7/Wednesday, with preceding moisture return across the southern
Plains setting up the potential for thunderstorms as this wave and
its associated cold front push eastward/southeastward across the
southern Plains. However, GEFS members show large differences on how
this wave progresses, with notable differences within the ECMWF
members too. Some members within both of these ensemble systems
suggest the development of a closed low over the Southwest instead
of progressive wave into the Plains. Consequently, as with the
earlier wave, predictability issues limit forecast confidence.

...Mosier.. 12/12/2024

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