Day 4-8 Severe Weather Outlook Issued on Jul 21, 2020
Updated: Tue Jul 21 09:00:03 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, Jul 24, 2020 - Sat, Jul 25, 2020
D7
Mon, Jul 27, 2020 - Tue, Jul 28, 2020
D5
Sat, Jul 25, 2020 - Sun, Jul 26, 2020
D8
Tue, Jul 28, 2020 - Wed, Jul 29, 2020
D6
Sun, Jul 26, 2020 - Mon, Jul 27, 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 210858
SPC AC 210858
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0358 AM CDT Tue Jul 21 2020
Valid 241200Z - 291200Z
...DISCUSSION...
A shortwave trough over the northern Plains and central Canada
should continue northeastward on Day 4/Friday, while impinging on an
upper ridge centered over the MS Valley. Strong instability is
forecast to develop across parts of the northern Plains into the
Upper Midwest, and storms that can develop in this environment may
become severe. At this point, there remains too much uncertainty in
the placement of greatest storm coverage to include 15% severe
probabilities. Some severe threat may continue on Day 5/Saturday
across portions of the northern Plains, Upper Midwest, and perhaps
Upper Great Lakes as another, stronger upper trough advances
eastward from western into central Canada. However, predictability
remains low regarding the timing/amplitude of this upper trough and
related surface features.
The large-scale upper trough centered over central Canada on Day
6/Sunday should shift eastward into eastern Canada and the Northeast
by early next week. Enhanced mid-level winds attendant to this upper
trough could support organized severe storms, although there is
potential for the stronger shear to remain displaced to the north of
a surface cold front. Regardless, some severe threat may occur
along/ahead of the front from then northern/central Plains into the
Upper Midwest and Great Lakes from Day 6/Sunday into Day 7/Monday. A
severe threat also appears possible across the Northeast early next
week. Still, far too much uncertainty exists at this extended time
frame to highlight specific areas with 15% or greater severe
probabilities.
..Gleason.. 07/21/2020
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