(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 231007
SPC AC 231007
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0407 AM CST Tue Jan 23 2018
Valid 261200Z - 311200Z
The 00Z ECMWF/GFS have great differences in the evolution of the Day
2/3 Pacific trough as it emerges from the Rockies into the Plains
and eastward this forecast period. The GFS maintains greater
consistency with itself, suggesting this trough will be progressive
and less amplified, while the latest ECMWF indicated slower eastward
movement and greater amplification across the eastern Plains and MS
Valley during the latter half of Day 5/Saturday. Despite this model
difference, the ECMWF ensemble suggested large spread with the
amplitude of the trough as it moves into the lower MS Valley,
central Gulf coast states and OH/TN Valleys during Day 6/Sunday.
A strong surface ridge extending westward across the Gulf coast
states to the lower MS Valley should limit the northward return of
Gulf moisture. If the ECMWF were to verify into Saturday, the
amplifying Pacific trough is expected to remain too far west of any
moisture return into East TX and the lower MS Valley. Thus, severe
potential remains low.
The limited moisture return inland with the ECMWF indicating weak
instability across the warm sector from the central Gulf coast
region to the Southeast states would suggest a low potential for
severe storms. However, given some indication for a more amplified
trough moving east through the lower MS Valley to the Southeast
states, this outlook will indicate a low predictability for severe
storms Day 6 to early Day 7/Monday.
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