SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0158 PM CST Sat Jan 01 2022
Valid 012000Z - 021200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PARTS OF
NORTHERN MS/AL...MIDDLE/EASTERN TN...FAR NORTHWEST GA...EXTREME
SOUTHEAST KY...
...SUMMARY...
Tornadoes, a couple of which could be strong, and damaging winds
will be possible through tonight, especially across the Tennessee
Valley.
...20Z Update...
The primary change to the outlook is to clear severe-hazard and
thunder probabilities in the wake of ongoing storms along the
convectively reinforced surface boundary. Otherwise, potential
remains for discrete supercell development within the warm sector,
especially across northern MS/AL into middle TN, though coverage of
any such activity remains uncertain. Any mature supercells ahead of
the surface boundary would pose a conditional threat for tornadoes,
including the potential for a strong tornado or two. Otherwise,
widespread convection along the primary surface boundary will pose a
threat for scattered damaging wind gusts and a couple of tornadoes
as it moves eastward into this evening. See the previous discussion
below for more information.
..Dean.. 01/01/2022
.PREV DISCUSSION... /ISSUED 1023 AM CST Sat Jan 01 2022/
...Ark-La-Tex to the TN Valley...
Convection has persisted along a baroclinic zone demarcating the
northwest edge of the richer low-level moisture from the Ark-La-Tex
into western TN/KY. The convection has reinforced this boundary with
modest pressure rises behind it, resulting in it receding southeast
in the Mid-South. It is very unlikely to return north, given the
lack of appreciable cyclogenesis as a result of an expansive cold
air mass across the central U.S. that will undercut the stronger
forcing for ascent in advance of the primary shortwave trough over
the Four Corners. Even though the main surface cyclone will not be
intense and will develop farther away from the warm sector (in
tandem with an ejecting shortwave trough over KS/OK), strong
deep-layer wind fields and vertical shear will persist through the
day and into tonight in the warm sector across the TN Valley.
Given the persistence of the subtropical ridge over FL and only
glancing/small height falls through the day, much of the convection
may remain confined to the convection-reinforced frontal zone.
Still, there will be the potential for embedded supercells within a
broken band of storms along the front, and a lower chance for a
few supercells in the open warm sector along diffuse confluence
zones a little south of the front later this afternoon/evening.
Effective bulk shear of 60-70 kt and MLCAPE of 500-1500 J/kg will
conditionally support supercells capable of producing tornadoes,
damaging winds, and marginally severe hail. The prospects for a
couple strong tornadoes will likely hinge on pre-frontal supercell
development that is not entirely undercut by the surface front. This
is most likely from northern portions of MS/AL into middle TN where
effective SRH in excess of 300 m2/s2 should be common late this
afternoon/evening. The frontal convection will spread southeast
through the overnight hours, with a gradually lessening severe
threat and shrinking warm sector centered on AL toward the end of
the period.
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