Day 4-8 Severe Weather Outlook Issued on Aug 9, 2020
Updated: Sun Aug 9 08:36:03 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
Wed, Aug 12, 2020 - Thu, Aug 13, 2020
D7
Sat, Aug 15, 2020 - Sun, Aug 16, 2020
D5
Thu, Aug 13, 2020 - Fri, Aug 14, 2020
D8
Sun, Aug 16, 2020 - Mon, Aug 17, 2020
D6
Fri, Aug 14, 2020 - Sat, Aug 15, 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 090833
SPC AC 090833
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0333 AM CDT Sun Aug 09 2020
Valid 121200Z - 171200Z
...DISCUSSION...
...Wednesday/Day 4 and Thursday/Day 5...
The medium-range models move a shortwave trough across the northern
High Plains on Wednesday. A corridor of moderate instability is
forecast across the central and northern Plains Wednesday afternoon.
Some solutions suggest that thunderstorm development may occur along
the western edge of the stronger instability in the western and
central Dakotas late Wednesday afternoon. If this scenario plays
out, then a severe threat would be possible across the Dakotas
during the late afternoon and early evening.
On Thursday, the models are in decent agreement with cyclonic
west-southwest mid-level flow located in the northern Plains. An
axis of moderate instability is forecast in the eastern Dakotas by
afternoon. In spite of this, the models keep the airmass capped
suggesting that convective coverage would remain sparse. If the cap
is weaker than forecast and convection does develop, then an
isolated severe threat can not be ruled out for parts of the
northern Plains Thursday afternoon and evening.
...Friday/Day 6 to Sunday/Day 8...
An upper-level trough is forecast to move across the northern
Rockies on Friday as a mid-level jet moves into the northern High
Plains. Although the ECMWF and GFS differ on the timing of the
upper-level trough, both solutions suggest convection could develop
by evening in parts of eastern North Dakota and northwestern
Minnesota. Forecast instability and shear would be strong enough for
an isolated severe threat under this scenario.
On Saturday and Sunday, the models are in good agreement, moving a
cold front southeastward across the upper Mississippi Valley and
into the Great Lakes region. Isolated severe thunderstorms could
develop along parts of the front each day. But uncertainty is
substantial at this range concerning various factors including the
magnitude of instability and the timing of the front.
..Broyles.. 08/09/2020
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