(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 270941
SPC AC 270941
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0341 AM CST Wed Jan 27 2021
Valid 301200Z - 041200Z
Medium-range models continue to exhibit reasonable large-scale
agreement with respect to evolution of the upper pattern, through
roughly Day 7. Beyond that, differences quickly arise with handling
of a large trough crossing the West late in the period.
Prior to then, the pattern aloft will be characterized by the
progression of a trough -- initially situated over the southern
Rockies/central and southern High Plains. As this feature
evolves/shifts eastward with time, it will be accompanied by a
well-developed surface low/frontal system, that models suggest will
move from the High Plains early Day 4 (Saturday), to near/off the
East Coast by the end of Day 6 (Tuesday morning).
Despite the well-developed nature of this surface system, its warm
sector will likely remain notably lacking in instability, due to the
antecedent cP airmass intrusion through the Gulf of Mexico, and
persistence of ridging aloft across the western Atlantic and into
the Gulf. As such, though precipitation -- including
weak/low-topped convection -- will accompany passage of the system,
severe weather is not expected.
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