(All days are valid from 12 UTC - 12 UTC the following day)
Note: A severe weather area depicted in the Day 4-8 period indicates 15%, 30% or higher probability for severe thunderstorms within 25 miles of any point.
PREDICTABILITY TOO LOW is used to indicate severe storms may be possible based on some model scenarios. However, the location or occurrence of severe storms are in doubt due to: 1) large differences in the deterministic model solutions, 2) large spread in the ensemble guidance, and/or 3) minimal run-to-run continuity.
POTENTIAL TOO LOW means the threat for a regional area of organized severe storms appears unlikely (i.e., less than 15%) for the forecast day.
Forecast Discussion
ZCZC SPCSWOD48 ALL
ACUS48 KWNS 040914
SPC AC 040914
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0314 AM CST Sat Dec 04 2021
Valid 071200Z - 121200Z
...DISCUSSION...
Modest amplification of the mid-level westerlies may occur over
portions of the central/eastern CONUS on Day 4/Tuesday into Day
5/Wednesday. Regardless, a prior frontal passage into the northern
Gulf of Mexico should generally inhibit the inland advance of
substantial low-level moisture along most of the Gulf Coast in this
time frame. Parts of FL and southern GA may be an exception, but
weak forecast instability should limit the threat for organized
severe convection.
Latest medium-range guidance is starting to come into better
agreement with the prospect for another upper trough to amplify and
move eastward across the western/central CONUS around Day 6/Thursday
into Day 7/Friday. If this occurs, then the related low-level mass
response would encourage the inland return of rich low-level
moisture from the Gulf of Mexico into parts of the Southeast and
perhaps even the OH Valley. Of course, there are differences in the
placement and evolution of this upper trough and attendant surface
features at this extended time frame. Still, an increase in severe
potential is evident based on some of the latest models for parts of
the lower MS Valley and Southeast on Day 8/Saturday. While it is too
soon to include a 15% severe delineation due to model differences
and inherent uncertainty, this scenario will be closely monitored.
..Gleason.. 12/04/2021
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