Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sun Mar 26 2023 08:20:46

ACUS48 KWNS 260820
SWOD48
SPC AC 260819

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0319 AM CDT Sun Mar 26 2023

Valid 291200Z - 031200Z

....DISCUSSION...
Severe potential will be low on Day 4/Wed as an upper ridge remains
over the Plains and an upper trough digs over the western U.S.
Surface high pressure over the Midwest will result in mostly stable
conditions as Gulf moisture remains offshore east of the Mississippi
River. Late in the period, the western trough will being to migrate
eastward. Developing low pressure over the Four Corners and southern
Rockies will result in increasing southerly low level flow over the
southern Plains, and Gulf moisture will begin to return northward
across TX by early Day 5/Thu.

Severe potential will increase markedly on Days 5-6/Thu-Fri from the
southern/central Plains toward the Mid/Lower Mississippi Valley
vicinity. The western upper trough is expected to slowly progress
eastward during this time. There remain differences in forecast
guidance regarding the timing of the upper trough ejecting east from
the western U.S. into the Plains and then eastward. While the GFS
suite of guidance remains faster than the ECMWF and Canadian
guidance, overall trends have become better aligned. Given timing
uncertainty, the severe delineations may still shift/expand in the
coming days. If a slower trough ejection occurs, the severe threat
on Thursday could become more isolated due to capping. Nevertheless,
a large warm sector will overspread the southern/central Plains into
the Mid-South vicinity Thursday and Friday. This will occur as a
deepening surface low over the southern/central High Plains ejects
east/northeast and intense low/midlevel southwesterly flow
overspreads the region. This should support severe thunderstorms
capable of all severe hazards shifting east/northeast with time from
the Plains toward the Mid/Lower MS Valley vicinity Thu/Fri.

Confidence in severe potential continuing into Day 7/Sat is low,
given aforementioned timing uncertainty and several bouts of
thunderstorms heading into the weekend. Forecast guidance
discrepancies only increase further heading into Day 8/Sun and
predictability is low.

...Leitman.. 03/26/2023

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