Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Thu Jun 08 2023 09:01:30

ACUS48 KWNS 080901
SWOD48
SPC AC 080859

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0359 AM CDT Thu Jun 08 2023

Valid 111200Z - 161200Z

....DISCUSSION...
Amplification of an upper trough over the MS Valley should occur on
Day 4/Sunday as a closed upper low develops across the Upper Midwest
and Great Lakes. Thunderstorms that can develop along/south of a
front across the lower/mid MS Valley and parts of Southeast could
become severe, given an unstable airmass and sufficient deep-layer
shear to support organized convection. Isolated severe thunderstorms
also appear possible across parts of north-central/east TX with any
convection that can initiate along a dryline. However, uncertainty
in frontal position and the potential negative effects of prior
days' convection suggest that inclusion of a 15% severe area for
Sunday would be premature at this time.

Some severe threat should exist on Day 5/Monday across a broad part
of the central/eastern CONUS, generally along/south of a front.
Delineating specific corridors of greater severe potential appears
highly uncertain due to prior convection and substantial differences
in guidance with the position of the front across the Plains and
Southeast Monday afternoon. Therefore, no severe areas have been
included for Monday.

A fair amount of spread remains in medium-range deterministic and
ensemble guidance regarding the evolution of an upper trough over
the western states early next week, and possible ejection of a
low-amplitude shortwave trough across the southern/central Plains,
lower/mid MS Valley, and Southeast from Day 6/Tuesday through Day
8/Thursday. If a more amplified and faster shortwave trough ejects
across these regions, then a substantial severe threat may exist for
multiple days in this time frame. However, some guidance continues
to show a slower and less amplified evolution of the shortwave
trough, which could delay and/or shift the primary severe risk much
farther south since the surface front would likely not return as far
north. There is still far too much spread in guidance, and
uncertainty regarding spatial placement of potential severe
thunderstorms, to include any 15% delineations at this extended time
frame. Regardless, trends will need to be closely monitored for
increasing severe potential across the southern/central Plains,
lower/mid MS Valley, TN Valley, and Southeast from Day 6/Tuesday
onward.

...Gleason.. 06/08/2023

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