(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 210849
SPC AC 210849
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0349 AM CDT Sun Jul 21 2019
Valid 241200Z - 291200Z
Weakening of the eastern U.S. upper-level trough early in the period
will result in a more zonal component to the mid/upper-level flow
across the CONUS, with the strongest winds confined to the northern
tier of states. Surface high pressure will build eastward in the
wake of a frontal boundary extending from FL west through south TX,
with a notably drier air mass over much of the central/eastern U.S.
contributing to low severe potential.
By Day 6/Friday and beyond, a couple of shortwave troughs within the
stronger flow aloft will affect areas from the northern Rockies east
to the Great Lakes. Although the severe threat will likely increase
during this time frame, predictability remains low due to
uncertainty regarding the timing of these features and spatial
distribution of instability/favorable shear.
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