Day 4-8 Severe Weather Outlook Issued on Aug 21, 2020
Updated: Fri Aug 21 08:40:03 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
Mon, Aug 24, 2020 - Tue, Aug 25, 2020
D7
Thu, Aug 27, 2020 - Fri, Aug 28, 2020
D5
Tue, Aug 25, 2020 - Wed, Aug 26, 2020
D8
Fri, Aug 28, 2020 - Sat, Aug 29, 2020
D6
Wed, Aug 26, 2020 - Thu, Aug 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 210838
SPC AC 210838
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0338 AM CDT Fri Aug 21 2020
Valid 241200Z - 291200Z
...DISCUSSION...
The latest runs of the medium-range models appear to be in
reasonable agreement overall with respect to the upper flow field
over the CONUS. In general, the pattern should trend toward
evolution of a broad/flat ridge over the central U.S. early in the
period, with low amplitude troughing over the northwestern and
northeastern portions of the country. Noteworthy during early
stages of the period are hints that a pair of tropical systems may
affect portions of the Gulf Coast states (please see the latest
tropical forecasts from the National Hurricane center for
information regarding tropical depressions 13 and 14).
With time, and perhaps partially assisted by the inland
advance/evolution of the tropical systems, ridging over the central
U.S. is expected to weaken, with a notable/gradual southward shift
-- and amplification of -- the main belt of westerlies into the U.S.
through the remainder of the period.
Given this uncertain pattern evolution, confidence is low with
respect to convective details. Convection -- and some severe
potential -- will likely linger over the north-central U.S. for the
first couple of days of the period (the early to middle portion of
next week) as short-wave disturbances moving through the weakly
anticylonic belt of enhanced westerlies aloft. Severe risk also may
persist over the Northeast Day 4/5 (Monday/Tuesday), as a fairly
pronounced cold front appears likely to cross the area (though
differences in timing/evolution are apparent from model to model).
With time, the trailing portion of this front is progged to sag
gradually southward across the central and eastern U.S., likely
serving as a focus for daily convective development, and possibly
some accompanying severe potential, through the end of the period.
..Goss.. 08/21/2020
CLICK TO GET WUUS48 PTSD48 PRODUCT
weather.gov 
@NWSSPC
