Day 4-8 Severe Weather Outlook Issued on Aug 7, 2020
Updated: Fri Aug 7 08:56:02 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, Aug 10, 2020 - Tue, Aug 11, 2020
D7
Thu, Aug 13, 2020 - Fri, Aug 14, 2020
D5
Tue, Aug 11, 2020 - Wed, Aug 12, 2020
D8
Fri, Aug 14, 2020 - Sat, Aug 15, 2020
D6
Wed, Aug 12, 2020 - Thu, Aug 13, 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 070853
SPC AC 070853
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0353 AM CDT Fri Aug 07 2020
Valid 101200Z - 151200Z
...DISCUSSION...
...Monday/Day 4 and Tuesday/Day 5...
The medium-range models including the ECMWF, GFS, UKMET and CANADIAN
begin the day 4 to 8 period with a long fetch of west-northwesterly
flow across the northwest and north-central United States. A
shortwave trough and associated cold front is forecast to move into
the western Great Lakes region on Monday where scattered strong
thunderstorms may develop. Forecast instability and deep-layer shear
suggest an isolated severe threat will be possible there Monday
afternoon and evening.
On Tuesday, the models keep westerly mid-level flow in place across
much of the northern states and show a corridor of moderate
instability across the central and northern Plains. Although
large-scale ascent may be weak across the north-central states,
thunderstorms could develop along the western edge of the stronger
instability, in parts of the northern Plains. Forecast deep-layer
shear in the northern Plains appears sufficient for an isolated
severe threat Tuesday afternoon and evening.
...Wednesday/Day 6 to Friday/Day 8...
On Wednesday, both the ECMWF and GFS move a shortwave trough into
the mid Mississippi Valley but have a shortwave ridge in the
northern Plains. The models maintain a corridor of moderate
instability in the central and northern Plains where isolated strong
thunderstorms will be possible. Forecast deep-layer shear again
appears sufficient for an isolated severe threat there Wednesday
afternoon and evening.
On Thursday and Friday, model forecasts diverge sharply. The
commonality among solutions is a corridor of low-level moisture and
instability from the mid Missouri Valley into the northern Plains.
Some solutions suggest an upper-level ridge will be in place in the
north-central U.S. This would keep convective coverage minimal.
However, uncertainty late in the period is substantial. Any storms
that can develop in the stronger instability could have an isolated
severe threat.
..Broyles.. 08/07/2020
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