(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 250750
SPC AC 250750
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0250 AM CDT Mon Sep 25 2017
Valid 281200Z - 031200Z
A shortwave trough will migrate southward across portions of the
Great Lakes through D4/Thursday and D5/Friday, while a weakening
cutoff low dissipates across the Intermountain West. At the
surface, an expansive ridge will spread a cooler, drier airmass of
continental origin across much of the central and eastern CONUS,
with deeper boundary layer moisture confined to Gulf Coast regions
south of a stationary front in that area. This overall pattern will
result in a minimal severe threat through at least D7/Sunday.
After D7, an active/amplified mid-level pattern across the northern
tier of the U.S. may interact with returning boundary layer moisture
on the western periphery of an anticyclone as it shifts toward the
East Coast. This pattern may eventually result in a returning
severe risk to the center of the country beyond the extended
forecast period although confidence is low.
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