Day 4-8 Severe Weather Outlook Issued on Sep 11, 2020
Updated: Fri Sep 11 08:07:02 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
Mon, Sep 14, 2020 - Tue, Sep 15, 2020
D7
Thu, Sep 17, 2020 - Fri, Sep 18, 2020
D5
Tue, Sep 15, 2020 - Wed, Sep 16, 2020
D8
Fri, Sep 18, 2020 - Sat, Sep 19, 2020
D6
Wed, Sep 16, 2020 - Thu, Sep 17, 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 110805
SPC AC 110805
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0305 AM CDT Fri Sep 11 2020
Valid 141200Z - 191200Z
...DISCUSSION...
Severe potential appears low for much of the Day 4-8 period. Upper
ridging will persist across the western states and over the
southeastern U.S. Progressive northern-stream flow will flatten the
upper ridge across the northern tier of the U.S., but guidance
varies on how far south any of the stronger upper shortwave troughs
across Canada may develop into the U.S. There is some indication
that a deeper trough may shift southeast from the Canadian Prairies
and track across the Midwest and then eastward across the eastern
states by the Day 7 or 8 time frame. If this occurs, a moist airmass
will be in place across the Midwest/Great Lakes vicinity, and
thunderstorm activity would be likely with any cold frontal passage.
However, confidence in this scenario, and any accompanying severe
potential, is low given disparity among forecast guidance.
..Leitman.. 09/11/2020
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