Day 4-8 Severe Weather Outlook Issued on Oct 20, 2020
Updated: Tue Oct 20 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
Fri, Oct 23, 2020 - Sat, Oct 24, 2020
D7
Mon, Oct 26, 2020 - Tue, Oct 27, 2020
D5
Sat, Oct 24, 2020 - Sun, Oct 25, 2020
D8
Tue, Oct 27, 2020 - Wed, Oct 28, 2020
D6
Sun, Oct 25, 2020 - Mon, Oct 26, 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 200854
SPC AC 200854
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0354 AM CDT Tue Oct 20 2020
Valid 231200Z - 281200Z
...DISCUSSION...
...Friday/Day 4 to Monday/Day 5...
On Friday, the medium-range models are in reasonable agreement,
moving an upper-level trough across the Intermountain West. At the
surface, a cold front is forecast to move southeastward into the
Ohio and mid Mississippi Valleys. Although instability is forecast
to be weak ahead of the front, a marginal severe threat can not be
ruled out Friday afternoon in pockets that destabilize the most.
On Saturday, the models continue in reasonable agreement with an
upper-level trough in the western U.S. and west-southwest mid-level
flow from the Great Plains to the Great Lakes. At the surface, a
cold front is forecast to be located from the lower Mississippi
Valley into the southern Appalachians. Instability along the front
is forecast to be very weak, suggesting that the severe threat could
be limited Saturday afternoon.
...Sunday/Day 6 to Tuesday/Day 8...
Model solutions diverge in the latter half of the Day 4 to 8 period.
Some solutions develop an upper-level trough across the southern
High Plains by Monday with other solutions keeping the trough
further west in Desert Southwest. The faster solutions suggest that
a large area of precipitation will develop from parts of the
southern Plains northeastward to the Ohio Valley from late Sunday
night into Monday. If this scenario pans out, then thunderstorms
would be possible along the northern edge of the moist sector on
Monday from parts of Texas east-northeastward to the Tennessee
Valley. The faster solutions suggest the thunderstorm potential
would continue into Tuesday as a cold front moves across the
southern Appalachians and Southeast. Under this scenario,
instability would be relatively weak along and ahead of the front
keeping any severe threat marginal. Predictability remains low late
in the Day 4 to 8 period.
..Broyles.. 10/20/2020
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