(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 200945
SPC AC 200945
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0345 AM CST Mon Nov 20 2017
Valid 231200Z - 281200Z
Models continue to indicate the synoptic upper pattern will remain
dominated by a mean trough over the eastern U.S. with an upstream
ridge in the west. Overall severe threat should be low in this
regime. At least a marginal severe threat could evolve over FL from
late day 4 (Thursday) to day 5 (Friday) when models indicate a
vorticity maximum moving through the base of the southern-stream
trough will induce a weak cyclone over the eastern Gulf, along with
some increase in vertical shear near a warm/stationary front.
However, solutions continue to differ regarding the strength of this
feature, and the thermodynamic environment will likely remain very
marginal which lowers overall predictability and severe potential.
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