Nashville, TN...Shreveport, LA...Columbus, GA...Little Rock, AR...Huntsville, AL...
Day 5 Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
15 %
125,018
15,375,744
Jacksonville, FL...Virginia Beach, VA...Raleigh, NC...Norfolk, VA...Greensboro, NC...
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, Mar 17, 2021 - Thu, Mar 18, 2021
D7
Sat, Mar 20, 2021 - Sun, Mar 21, 2021
D5
Thu, Mar 18, 2021 - Fri, Mar 19, 2021
D8
Sun, Mar 21, 2021 - Mon, Mar 22, 2021
D6
Fri, Mar 19, 2021 - Sat, Mar 20, 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 140908
SPC AC 140908
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0408 AM CDT Sun Mar 14 2021
Valid 171200Z - 221200Z
...DISCUSSION...
Medium-range models have come into somewhat better agreement with
respect to synoptic features through the early half of the period,
though smaller-scale differences persist. Still, confidence has
increased that a fairly widespread severe weather event will occur
Day 4 (Wednesday) across the lower Mississippi Valley/central Gulf
Coast region and northward into at least parts of the Tennessee
Valley, and then continuing into Day 5 (Thursday) east of the
Appalachians. In the wake of this severe-weather episode, high
pressure/stable air should spread across the U.S. east of the
Rockies, yielding at least a couple of days of quieter weather with
respect to convective potential.
On Wednesday, convection will likely be ongoing across the eastern
Texas/Arkansas/Louisiana areas, with some severe risk possible
during the morning hours. By afternoon, an increase in coverage and
intensity is expected as closed upper system shifts out of the
Plains toward the Mississippi Valley. With a rather
large/destabilizing warm sector and ample shear across a broad
region, a rather large 15% area will be maintained, representative
of an all-hazards severe risk. Corridors of greater risk --
including possibly more concentrated tornado potential -- may evolve
during the afternoon, possibly near the northward-moving warm front.
While the ECMWF is farther south with this west-to-east front
(central MS/AL) during the afternoon than the GFS (southern TN),
will nonetheless introduce a 30% risk area -- encompassing a range
of possible warm-frontal locations -- given likelihood for
widespread severe weather that warrants greater probability at this
time.
The severe risk may diminish some into the evening/overnight across
the southern Appalachians area, but should increase somewhat
Thursday east of the mountains, possibly as far north as southern
Virginia and extending southward into north Florida. Timing
differences in progression of the surface front increase between the
GFS and ECMWF with time, so when the threat finally subsides -- as
storms move offshore -- remains uncertain. However, this should
certainly occur prior to the start of Day 6 (Friday), resulting in
what appears likely to be at least a couple of days of substantially
decreased convective potential.
..Goss.. 03/14/2021
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