Day 4-8 Severe Weather Outlook Issued on Apr 22, 2021
Updated: Thu Apr 22 09:00:03 UTC 2021
Day 4 Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 5 Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 6 Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
15 %
149,477
12,113,531
Dallas, TX...Fort Worth, TX...Oklahoma City, OK...Tulsa, OK...Arlington, TX...
Day 7 Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 8 Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
D4
Sun, Apr 25, 2021 - Mon, Apr 26, 2021
D7
Wed, Apr 28, 2021 - Thu, Apr 29, 2021
D5
Mon, Apr 26, 2021 - Tue, Apr 27, 2021
D8
Thu, Apr 29, 2021 - Fri, Apr 30, 2021
D6
Tue, Apr 27, 2021 - Wed, Apr 28, 2021
(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.
Forecast Discussion
ZCZC SPCSWOD48 ALL
ACUS48 KWNS 220858
SPC AC 220858
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0358 AM CDT Thu Apr 22 2021
Valid 251200Z - 301200Z
...DISCUSSION...
An upper trough is forecast to move off the East Coast early on Day
4/Sunday, with rich low-level moisture and boundary-layer
instability confined to parts of the FL Peninsula to the south of a
cold front. Both low and mid-level flow should veer to westerly
behind the upper trough passage. This should limit low-level
convergence along the surface front, and organized severe
thunderstorm potential appears low on Day 4/Sunday. Latest
medium-range guidance remains in remarkably good agreement with the
progression of an upper trough over the western CONUS from Day
4/Sunday into Day 5/Monday. If this upper trough evolves as
forecast, then lee cyclogenesis across the southern/central High
Plains should occur early next week. Rich Gulf moisture should
advect northward across the southern/central Plains to the east of a
sharpening dryline from Day 5/Monday into Day 6/Tuesday.
The run-to-run consistency of the ECMWF continues, with the latest
run indicating the development of moderate to strong instability
east of the dryline by Tuesday afternoon across central TX into
western/central OK and parts of KS. As the upper trough ejects
across the Plains, an enhanced mid-level jet should overspread the
dryline and warm sector. Large-scale ascent associated with the
upper trough and low-level convergence along the dryline appear
sufficient to initiate convection by Tuesday afternoon. If this
occurs, then an organized severe thunderstorm threat will develop,
with all severe hazards possible. The 15% severe area for Tuesday
has been expanded to include most of the length of the dryline where
severe thunderstorms appear possible. Expect adjustments to this
area in the coming days, including the potential for greater severe
probabilities, as additional model guidance comes in.
For Day 7/Wednesday and Day 8/Thursday, confidence is not high
enough to introduce 15% severe probabilities. Depending on Tuesday's
convection and the quality of low-level moisture return ahead of the
eastward-moving upper trough/low, some severe threat may exist on
Day 7/Wednesday across parts of the lower/mid MS Valley. But,
predictability is low at this extended time frame.
..Gleason.. 04/22/2021
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