(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 250851
SPC AC 250851
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0251 AM CST Sun Feb 25 2018
Valid 281200Z - 051200Z
...Wednesday/Day 4 to Thursday/Day 5...
The medium-range models including the ECMWF, GFS, UKMET and Canadian
move an upper-level trough from the Desert Southwest into the
Rockies on Wednesday. A moist airmass is forecast to be in place
from the southern Plains eastward into the lower Mississippi Valley.
The development of strong to severe thunderstorms may occur on
Wednesday or Wednesday night from northeast Texas east-northeastward
into the lower to mid Mississippi Valley as the exit region of a
strong mid-level jet approaches. This feature along with a low-level
jet in the Arklatex is forecast to create favorable shear profiles
for organized severe storms including supercells and fast moving
line-segments. A few tornadoes and some wind damage will be
possible. The models move the upper-level trough quickly eastward
into the Mississippi Valley on Thursday as a cold front advances
southeastward across the southern Appalachians. Ahead of this front,
some severe convection will be possible mainly from the eastern Gulf
Coast States northeastward into the Carolinas but predictability
...Friday/Day 6 and Sunday/Day 8...
On Friday, all four solutions move an upper-level low across the
Mid-Atlantic and into the western Atlantic as a cold front advances
southward into the northern Gulf of Mexico. A dry airmass is
forecast to overtake most of the CONUS on Friday into Saturday
making thunderstorm potential low. On Sunday, the models have an
upper-level ridge over the east-central U.S. and show moisture
return taking place in Texas and Louisiana. Although a marginal
severe threat can not be ruled out on Sunday across parts of the
south-central U.S., the spread among solutions is large suggesting
predictability is low on Sunday.
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