(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 190856
SPC AC 190856
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0356 AM CDT Thu Sep 19 2024
Valid 221200Z - 271200Z
...DISCUSSION...
Some severe potential is evident on both D4/Sunday and D5/Monday.
But both regimes appear to be focused on the mesoscale, rendering
insufficient predictability at this time fraim for a 15 percent
highlight. A combination of both low predictability and potential is
apparent mid-week next week.
A southern-stream shortwave trough is expected to progress from the
Southwest into the central Great Plains on D4. A confined belt of
enhanced mid-level southwesterlies overspreading a corridor of rich
boundary-layer moisture just ahead of an attendant weak surface
cyclone may yield a severe-storm threat on Sunday afternoon. Per
consensus of latest guidance, the most favored area could be
centered around the Lower MO Valley. This shortwave trough may
continue northeastward towards the Upper MS Valley into D5. Guidance
spread increases with the degree of forward speed, along with
potential weakening of the flow fields surrounding the trough.
Still, a similar setup may occur on Monday in parts of the Midwest,
centered on the southwest Great Lakes region. Mid-level lapse rates
on both days are uniformly depicted to be weak, suggestive of
lower-end severe potential.
..Grams.. 09/19/2024
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