(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 240956
SPC AC 240956
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0356 AM CST Sat Feb 24 2018
Valid 271200Z - 041200Z
...Tuesday/Day 4 to Thursday/Day 6...
The medium-range models including the ECMWF, GFS, UKMET and Canadian
move an upper-level ridge across the eastern states on Tuesday as
moisture return takes place in the southern Plains and lower
Mississippi Valley. A marginal severe threat will be possible in the
warm advection regime across the Arklatex on Tuesday but the
magnitude of the threat remains uncertain. On Wednesday, an
upper-level trough is forecast to move across northern Mexico. Ahead
of this system, some severe thunderstorms will be possible from the
southern Plains into the Arklatex on Wednesday as a low-level jet
persists across east Texas. The low-level jet is forecast to shift
northeastward into the lower Mississippi Valley Wednesday night
where a severe threat may also occur. The 15 percent contour is
maintained to account for this potential. On Thursday, the
upper-level trough is forecast to move across the south-central U.S.
although the ECMWF and UKMET are much slower with the shortwave
trough. This seems reasonable which would place the best chance of
severe storms in the lower Mississippi Valley and central Gulf Coast
states Thursday afternoon. The preferred location for severe storms
will depend upon the timing of the upper-level trough.
...Friday/Day 7 and Saturday/Day 8...
On Friday, the models move the upper-level trough off the Southeast
coast into the western Atlantic as a cold front moves into the Gulf
of Mexico. A dry airmass is forecast to be in place across most of
the CONUS on Friday into Saturday. For this reason, the potential
for thunderstorm development appears low late in the day 4 to 8
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