Day 4-8 Severe Weather Outlook Issued on Aug 11, 2020
Updated: Tue Aug 11 07:54:03 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, Aug 14, 2020 - Sat, Aug 15, 2020
D7
Mon, Aug 17, 2020 - Tue, Aug 18, 2020
D5
Sat, Aug 15, 2020 - Sun, Aug 16, 2020
D8
Tue, Aug 18, 2020 - Wed, Aug 19, 2020
D6
Sun, Aug 16, 2020 - Mon, Aug 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 110752
SPC AC 110752
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0252 AM CDT Tue Aug 11 2020
Valid 141200Z - 191200Z
...DISCUSSION...
...Friday/Day 4 and Saturday/Day 5...
The medium-range models including the ECMWF, GFS, UKMET and Canadian
are in general agreement, moving a cold front from the northern
Plains into the Upper Mississippi Valley on Friday. Thunderstorm
development will be possible along and ahead of the front during the
afternoon and evening. The models suggest that instability and
deep-layer shear will be sufficient for a severe threat. However,
uncertainty exists concerning the distribution of instability and
timing of the front, so a forecast area can not be added at this
time.
From Saturday into Saturday night, the models move an upper-level
trough across the north-central states. An associated cold front is
also forecast to move southeastward across parts of the Upper
Midwest. Thunderstorms will again be possible along the front, with
some having the potential to be severe. The model solutions vary on
the exact timing of the front. For this reason, uncertainty is
substantial concerning the magnitude and spacing of any severe
threat for Saturday.
...Sunday/Day 6 to Tuesday/Day 8...
From Sunday to Tuesday, the models move an upper-level trough across
the Great Lakes region as a cold front advances southeastward from
the central U.S. into the Southeast. A moist airmass is forecast
ahead of the front which could make isolated severe thunderstorms
possible each afternoon and evening. The severe threat would be
possible from near the front southeastward across parts of the
unstable airmass. Considering that deep-layer shear is forecast to
be weak across much of the central and southeastern U.S. any wind
damage threat would probably remain unorganized. However,
uncertainty is considerable late in the day 4 to 8 period.
..Broyles.. 08/11/2020
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