Day 4-8 Severe Weather Outlook Issued on Aug 31, 2020
Updated: Mon Aug 31 08:41:02 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
Thu, Sep 03, 2020 - Fri, Sep 04, 2020
D7
Sun, Sep 06, 2020 - Mon, Sep 07, 2020
D5
Fri, Sep 04, 2020 - Sat, Sep 05, 2020
D8
Mon, Sep 07, 2020 - Tue, Sep 08, 2020
D6
Sat, Sep 05, 2020 - Sun, Sep 06, 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 310839
SPC AC 310839
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0339 AM CDT Mon Aug 31 2020
Valid 031200Z - 081200Z
...DISCUSSION...
...Thursday/Day 4 and Friday/Day 5...
The medium-range models including the ECMWF, GFS, Canadian and UKMET
move a low-amplitude upper-level trough across the eastern third of
the U.S. on Thursday and Friday. At the surface, a moist airmass
will be in place in much of the Southeast. Moderate instability will
likely develop across much of the moist airmass both Thursday and
Friday afternoon. Thunderstorms that develop in proximity to the
strongest instability may have an isolated severe threat. However,
the details concerning any scenario for both days remains very
uncertain at this time.
...Saturday/Day 6 to Monday/Day 8...
On Saturday, the models advect low-level moisture northward into
parts of the upper Mississippi Valley. A fast-moving upper-level
trough is forecast to pass through the northern High Plains on
Saturday. Ahead of the approaching upper-level trough, a severe
threat may develop in parts of the upper Mississippi Valley, where
there is a chance of moderate instability and strong deep-layer
shear. The upper-level trough is forecast to move quickly eastward
into the upper Mississippi Valley on Sunday as a cold front advances
eastward into the Great Lakes region. Strong thunderstorms will be
possible Sunday afternoon along parts of the front where a severe
threat can not be ruled out. The front is forecast to move
southeastward across the Ohio and Tennessee Valley on Monday, once
again providing a focus for strong thunderstorm development. But
uncertainty is substantial on both Sunday and Monday.
..Broyles.. 08/31/2020
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