Day 4-8 Severe Weather Outlook Issued on Mar 18, 2021
Updated: Thu Mar 18 08:36:07 UTC 2021
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
Sun, Mar 21, 2021 - Mon, Mar 22, 2021
D7
Wed, Mar 24, 2021 - Thu, Mar 25, 2021
D5
Mon, Mar 22, 2021 - Tue, Mar 23, 2021
D8
Thu, Mar 25, 2021 - Fri, Mar 26, 2021
D6
Tue, Mar 23, 2021 - Wed, Mar 24, 2021
(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 180834
SPC AC 180834
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0334 AM CDT Thu Mar 18 2021
Valid 211200Z - 261200Z
...DISCUSSION...
Medium-range models are in general agreement on the large scale,
that a western U.S. trough will evolve through the period, with
several smaller-scale perturbations ejecting eastward across the
central and eastern U.S. through the period. However, details
regarding location, progression, and intensity of these
smaller-scale troughs are different within the different model
solutions. This casts considerable uncertainty with respect to the
medium-range convective forecast -- uncertainty which increases
steadily with time through Day 8.
Even with the advance of the first of these smaller-scale
disturbances -- expected to dig across California into the Southwest
Day 4/Sunday, and then move into the Plains Day 5 -- differences are
substantial, and are reflected notably in evolution of the surface
pattern east of the Rockies. With that said, it continues to appear
that quality of moisture return ahead of this system should remain
insufficient for appreciable severe risk through Day 5.
Beyond Day 5, this initial feature is expected to shift
northeastward and weaken, in response to the next feature digging
across the West. However, degree of spread within the model
solutions from Day 6 onward suggests very minimal predictability,
and thus no convective assessment will be rendered at this time.
..Goss.. 03/18/2021
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