(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 200937
SPC AC 200937
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0337 AM CST Tue Feb 20 2018
Valid 231200Z - 281200Z
Model consensus is that a significant shortwave trough will eject
northeast through the central Plains and middle MS Valley region
(Day 5) Saturday and Saturday night. Some deamplification of this
feature is expected, but model differences persist. GFS maintains a
more amplified trough with a deeper surface low suggesting the
potential for a greater severe threat compared to ECMWF, UKMET and
the Canadian. In either case a few severe storms might evolve in
vicinity of frontal zone from east TX into the lower MS and TN
Valley region as the low-level jet strengthens and shifts northeast
in response to the approaching shortwave trough. Storms may be
ongoing along baroclinic zone over a portion of this region, with
potential to intensify within zone of modest destabilization and
forcing associated with the migrating low-level jet. Limiting
factors are likelihood of widespread clouds and tendency for the
approaching shortwave trough to weaken with deeper forcing likely
remaining northwest of warm sector.
Some severe threat might linger into day 6, but overall potential
should decrease later day 6 into day 7 as a cold front moves into
the northern Gulf coast area.
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