Day 4-8 Severe Weather Outlook Issued on Sep 23, 2020
Updated: Wed Sep 23 08:44:02 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
Sat, Sep 26, 2020 - Sun, Sep 27, 2020
D7
Tue, Sep 29, 2020 - Wed, Sep 30, 2020
D5
Sun, Sep 27, 2020 - Mon, Sep 28, 2020
D8
Wed, Sep 30, 2020 - Thu, Oct 01, 2020
D6
Mon, Sep 28, 2020 - Tue, Sep 29, 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 230842
SPC AC 230842
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0342 AM CDT Wed Sep 23 2020
Valid 261200Z - 011200Z
...DISCUSSION...
Medium-range guidance is in reasonably good agreement that
large-scale upper troughing will develop and subsequently amplify
over the eastern CONUS this upcoming weekend into early next week.
Meanwhile, a highly amplified upper ridge will likely develop over
the western states in the same time frame. A surface cold front
associated with the upper trough is forecast to move across parts of
the Midwest, OH Valley, and Northeast from Day 4/Saturday through
Day 6/Monday. Although mid-level flow should be quite strong as the
frontal passage occurs, low-level moisture and related instability
are forecast to remain rather limited. This casts uncertainty on
whether any meaningful severe risk will develop across these
regions. A reinforcing cold front attendant to another, stronger
surface low may move across much of the central/eastern CONUS in the
Day 6/Monday to Day 8/Wednesday time frame. Deep-layer shear should
be strong as this second front progresses east-southeastward.
However, instability may once again be fairly weak. Too much
uncertainty exists regarding the both degree of instability and
robust storm development with either cold front passage to include
any 15% severe areas at this time.
..Gleason.. 09/23/2020
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