Day 4-8 Severe Weather Outlook Issued on Dec 13, 2020
Updated: Sun Dec 13 09:09:03 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, Dec 16, 2020 - Thu, Dec 17, 2020
D7
Sat, Dec 19, 2020 - Sun, Dec 20, 2020
D5
Thu, Dec 17, 2020 - Fri, Dec 18, 2020
D8
Sun, Dec 20, 2020 - Mon, Dec 21, 2020
D6
Fri, Dec 18, 2020 - Sat, Dec 19, 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 130907
SPC AC 130907
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0307 AM CST Sun Dec 13 2020
Valid 161200Z - 211200Z
...DISCUSSION...
A significant, remnant short wave perturbation, accelerating out of
the southern Great Plains by Tuesday, may reach the southern Mid
Atlantic coast by Wednesday evening. As it approaches the coast,
medium-range models indicate that it will support substantive
further deepening of a frontal wave initially developing off the
South Carolina coast by daybreak Wednesday. It might not be
entirely out of the question that a moistening and destabilizing
warm sector boundary layer could spread across parts of the North
Carolina Outer and Inner Banks vicinity Wednesday afternoon or
evening. However, at this point, this seems a low probability, and
it is not clear that this would support more than a low severe
thunderstorm risk.
Otherwise, mid/upper flow is forecast to become more zonal across
Canada later this week through next weekend, with much of the U.S.
remaining under the influence of branching westerlies emanating from
the mid-latitude Pacific. It appears that this may include a number
of relatively fast moving short wave perturbations. While the
potential for significant surface cyclogenesis appears low, even if
one of these is able to support at least modest cyclogenesis near
Gulf coastal areas, it is not clear that the Gulf boundary layer
will be able to modify sufficiently to support a substantive inland
return flow of moisture.
..Kerr.. 12/13/2020
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