Day 4-8 Severe Weather Outlook Issued on Dec 26, 2020
Updated: Sat Dec 26 10:00:04 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
Tue, Dec 29, 2020 - Wed, Dec 30, 2020
D7
Fri, Jan 01, 2021 - Sat, Jan 02, 2021
D5
Wed, Dec 30, 2020 - Thu, Dec 31, 2020
D8
Sat, Jan 02, 2021 - Sun, Jan 03, 2021
D6
Thu, Dec 31, 2020 - Fri, Jan 01, 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 260957
SPC AC 260957
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0357 AM CST Sat Dec 26 2020
Valid 291200Z - 031200Z
...DISCUSSION...
...Tuesday/Day 4 and Wednesday/Day 5...
The medium-range models move an upper-level trough across the Four
Corners region on Tuesday as a low-level jet strengthens in the
Great Plains. A cold front is forecast to move southeastward into
the central Plains as a surface low moves northeastward into the mid
Missouri Valley. Thunderstorm development will be possible along and
ahead of the front from Kansas southward into Oklahoma and Texas
during the late afternoon and evening. Weak moisture return should
minimize the severe potential in most areas. The greatest severe
threat may be confined to north-central Texas where surface
dewpoints could reach the mid to upper 50s F.
The upper-level trough is forecast to move eastward across the High
Plains on Wednesday as the cold front advances quickly southeastward
into the Arklatex and mid Mississippi Valley. Model forecasts
suggest a line of thunderstorms will be likely ahead of the front
during the afternoon. As this line interacts with a moist airmass
over the lower Mississippi Valley during the afternoon, a severe
threat could develop. Although instability is forecast to remain
weak, strong large-scale ascent and abundant deep-layer shear may be
sufficient for a wind damage threat. At this time, the greatest
potential would be in east Texas eastward across southern Louisiana
during the late afternoon. Uncertainty is significant and if
instability remains very weak ahead of the line, then the severe
threat could be minimal.
...Thursday/Day 6 to Saturday/Day 8...
Model forecasts move the upper-level trough into the lower
Mississippi Valley on Thursday as the moist sector shifts eastward
across the eastern Gulf Coast states. Thunderstorms will be possible
Thursday ahead a cold front from Mississippi eastward to Georgia.
Storm development could also occur in parts of the Carolinas. The
greatest potential for a severe threat would be in Georgia where
surface dewpoints are forecast to reach the 60s F. If instability
remains very weak across the moist sector, any severe threat could
be minimal.
On Friday and Saturday, a progressive upper-level trough is forecast
to move from the southern Rockies eastward to the lower Mississippi
Valley. Model forecasts suggest that moisture return ahead of the
system will be minimal, which could limit any severe potential ahead
of the trough.
..Broyles.. 12/26/2020
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