(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 240957
SPC AC 240957
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0357 AM CST Fri Feb 24 2017
Valid 271200Z - 041200Z
The upper pattern for the extended period will feature a large-scale
trough over the western U.S. which will move downstream into the
central U.S. on Tuesday (Day 5) and into the Great Lakes/Northeast
on Wednesday (Day 6). Following this disturbance, northwest flow
from the Canadian prairie provinces and offshore flow over the
central Gulf states will result in low potential for severe
thunderstorms for Thursday-Friday (Days 7-8). There is some risk
for severe thunderstorms beginning on Monday (Day 4) over the
central Gulf Coast states but the timing and low-amplitude character
of the disturbances which would influence thunderstorm development
remains uncertain at this time.
The 24/00z GFS appears to be an outlier in the timing of the
ejecting mid-level disturbance compared to the 24/00z ECMWF, CMC,
and UKMET deterministic models by 12 hours. The 24/00z MREF
ensemble consensus agreed more with the ECMWF, CMC, and UKMET in
timing of the impulse. Several days of return flow, coupled with
steepening lapse rates over the southern Great Plains and strong
shear, suggest severe thunderstorms are possible. Greater
confidence in the potential for a concentrated area of severe
thunderstorms seems to be centered on Tuesday and Tuesday night (Day
5) over AR and portions of the lower MS Valley.
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