(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.
ZCZC SPCSWOD48 ALL
ACUS48 KWNS 170842
SPC AC 170842
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0342 AM CDT Fri Sep 17 2021
Valid 201200Z - 251200Z
Modestly amplified mid-level troughing is forecast to progress east
of the northern Rockies early next week, and may undergo further
amplification while slowly continuing across and east of the
Mississippi Valley through the middle to latter portion of next
week. As it does, it appears that a fairly significant surface cold
front may surge out ahead of the stronger mid-level cold pool and
forcing for ascent, and the most prominent surface cyclogenesis may
occur near/east of the James/Hudson Bay vicinity. A remnant plume
of warm elevated mixed-layer air probably will be eroded/overturned
across the Great Plains, and generally weak destabilization (at
least where stronger shear and forcing for ascent become focused)
probably will be a mitigating factor concerning the risk for severe
weather. While thunderstorms posing at least some risk for severe
weather may be possible along/ahead of the front, the overall severe
weather potential appears relatively low at this time.
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