(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 200912
SPC AC 200912
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0312 AM CST Mon Feb 20 2017
Valid 231200Z - 281200Z
Medium-range deterministic models continue to show good run-to-run
consistency in their depiction of a powerful speed max ejecting into
the Great Plains on Thursday (Day 4) and subsequently moving
downstream into the OH Valley and southern Great Lakes on Friday
(Day 5). A deep surface cyclone will develop northeastward from the
central Great Plains to the southwestern Great Lakes vicinity on
Friday. Models show the advection of an elevated mixed layer and a
dryline into IL with a cold front eventually overtaking the boundary
and rapidly surging east-northeast. This outlook has accounted for
possible diurnal warm-sector development near the surface low and
the possibility for a strongly forced squall line posing a risk for
damaging winds. Models variability increases by Sunday (Day 7) and
Monday (Day 8) on the evolution of a possible disturbance moving
eastward from the southern Great Plains and affecting parts of the
MS Valley during this timeframe.
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