(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 210744
SPC AC 210744
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0244 AM CDT Sat Sep 21 2019
Valid 241200Z - 291200Z
On Tuesday/D4, a broad upper trough is forecast to dive
southeastward across northern Rockies and Plains, with substantial
cooling aloft and increasing wind fields. A cold front will
accompany this system, and should extend roughly from MN into NE.
Models differ on timing of the leading shortwave, with the ECMWF
relatively slow with the development of precipitation along the
front. As such, predictability is too low for D4 but severe
probabilities for hail and wind may be added in later outlooks. A
continuation of scattered storms is expected into Wednesday/D5 as
the cold front progresses east, with a lesser threat of severe
storms from KS into IL.
For the D6-D8 period, the upper low over the Southwest will
eventually eject northeast across the Plains, and may provide a
focus for a few severe storms on D6 or D7, though predictability is
quite low. Beyond this time frame, a large-scale trough
amplification over the West is likely, with warm and moist
conditions over much of the Plains.
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