(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 020841
SPC AC 020841
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0341 AM CDT Thu Nov 02 2017
Valid 051200Z - 101200Z
Although model timing differences exist, trends continue to point to
severe thunderstorms capable of large hail, damaging wind and
isolated tornadoes on Sun/D4, roughly from Illinois into Ohio. A
broad area of cyclonic flow aloft with dual/parallel shortwave
troughs will affect the upper and middle MS Valleys, and points east
including the Great Lakes region. Some early day storms may exist
across the region as southerly winds create lift near a warm front,
but the main severe weather threat will be near the surface low and
cold front as it sweeps eastward from Sunday afternoon into Monday
morning. Cold temperatures aloft, a capping inversion over the warm
sector and long hodographs suggest supercells may be the dominant
storm mode, creating damaging hail and wind. A few tornadoes will
also be possible given a 50 kt low-level jet, and most likely with
any supercells that can track eastward along the intersection of the
cold front and warm front/outflow boundary.
By Mon/D5, the cold front will continue across the Northeast, but
with much less instability to work with. However, numerous storms
and modest wind fields suggest at least some marginal wind damage
potential. Beyond D5, model solutions diverge rapidly with a
progressive pattern persisting.
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