Day 4-8 Severe Weather Outlook Issued on Sep 22, 2020
Updated: Tue Sep 22 08:32:02 UTC 2020
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
No Risk Areas Forecast
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
Fri, Sep 25, 2020 - Sat, Sep 26, 2020
D7
Mon, Sep 28, 2020 - Tue, Sep 29, 2020
D5
Sat, Sep 26, 2020 - Sun, Sep 27, 2020
D8
Tue, Sep 29, 2020 - Wed, Sep 30, 2020
D6
Sun, Sep 27, 2020 - Mon, Sep 28, 2020
(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 220830
SPC AC 220830
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0330 AM CDT Tue Sep 22 2020
Valid 251200Z - 301200Z
...DISCUSSION...
An upper trough should advance eastward from the Pacific Northwest
and northern Rockies to the northern/central Plains on Day 4/Friday.
Low-level moisture is forecast to gradually increase ahead of this
feature across parts of the Plains into the Upper Midwest and MS
Valley. Warm mid-level temperatures may keep the warm sector capped
across the Upper Midwest through much of the day Friday, although
deep-layer shear is forecast to be rather strong. Still, elevated
storms with a marginal severe threat may develop Friday night across
a portion of this region as a low-level jet strengthens.
The upper trough should continue eastward in tandem with a surface
cold front this upcoming weekend. However, substantial differences
in medium-range guidance emerge by Day 5/Saturday regarding the
timing/amplitude of this trough, related surface features, and the
degree of low-level moisture return. Depending on the upper trough's
evolution, an isolated/marginal severe risk may exist across parts
of the southern and eastern CONUS from Day 5/Saturday into early
next week. Regardless, far too much uncertainty exists to include
15% severe probabilities at this extended time frame.
..Gleason.. 09/22/2020
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