Day 4-8 Severe Weather Outlook Issued on Dec 16, 2020
Updated: Wed Dec 16 09:02:04 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
Sat, Dec 19, 2020 - Sun, Dec 20, 2020
D7
Tue, Dec 22, 2020 - Wed, Dec 23, 2020
D5
Sun, Dec 20, 2020 - Mon, Dec 21, 2020
D8
Wed, Dec 23, 2020 - Thu, Dec 24, 2020
D6
Mon, Dec 21, 2020 - Tue, Dec 22, 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 160900
SPC AC 160900
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0300 AM CST Wed Dec 16 2020
Valid 191200Z - 241200Z
...DISCUSSION...
Based on the latest model output, low pattern predictability appears
an increasing concern through this period. Short wave developments,
within branching flow downstream of a strong mid/upper jet across
the southern mid-latitude/subtropical Pacific, are becoming more
unclear. In general, though, guidance continues to suggest that
there will be increasing amplification within the flow, probably
including a prominent building mid-level ridge near the Pacific
coast by early next week. It appears that this may be followed by
downstream large-scale upper trough amplification across the central
and eastern U.S., perhaps accompanied by strong surface cyclogenesis
east of the middle Missouri Valley through the Great Lakes region by
the middle of next week.
If this occurs, large-scale forcing for ascent and strengthening
deep-layer wind fields and shear within the evolving warm sector
probably will become at least conditionally supportive of increasing
severe weather potential, somewhere east of the Mississippi Valley
into the Appalachians. It does still seem unlikely that there will
be opportunity for deep boundary-layer moistening over the Gulf of
Mexico, and substantive inland return flow to the warm sector, by
this time. While this may tend to minimize severe weather potential
with vigorous, deep convective development, it is possible that the
environment could still become conducive to damaging surface gust
potential enhanced by an evolving pre-cold frontal low-topped
convective line.
..Kerr.. 12/16/2020
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