(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 220901
SPC AC 220901
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0401 AM CDT Thu Jun 22 2023
Valid 251200Z - 301200Z
...DISCUSSION...
A shortwave trough is forecast to progress from the Mid/Upper MS
Valley into the Upper Great Lakes/Lower OH Valley on D4/Sunday,
before then continuing eastward through more of the OH and TN
Valleys on D5/Monday. Thunderstorm development is expected across
the Lower OH Valley during the afternoon, as cold front associated
with the shortwave trough moves through. There is some uncertainty
regarding the amount of destabilization that occurs prior to the
frontal passage, but strong mid-level flow will be spreading into
the region. This combination of ascent (both along the front and via
the approaching shortwave trough), buoyancy, and shear should be
enough to produce severe thunderstorms. Highest probability of
severe is currently expected across central/southern IN, southwest
KY, far southeast IL, and far northwestern TN.
Guidance offers differing solutions regarding the progression of the
shortwave on D5/Monday. A faster solution would take the wave and
associated stronger flow into the Mid-Atlantic, with an attendant
risk for severe thunderstorms. However, a slower solution favors
weakening mid-level flow and a less progressive cold front. This
variability limits forecast confidence, precluding the introduction
of any outlook areas.
Upper ridging is expected to build across the central CONUS from
D6/Tuesday through D8/Thursday. A shortwave trough is expected to
move through the northern periphery of this ridging during this time
frame. Some severe potential exists with this wave, but guidance
differs on its timing and location, limiting predictability.
..Mosier.. 06/22/2023
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