Day 4-8 Outlook
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0258 AM CST Wed Jan 12 2022
Valid 151200Z - 201200Z
...DISCUSSION...
Models are in relatively good agreement regarding severe-weather
potential through most of the D4-D8 period, with the primary feature
of interest being an intense shortwave trough that will affect the
Gulf Coast and southeastern states.
Starting on Saturday/D4, a shortwave trough is forecast to drop
southeast across the southern Plains, approaching the lower MS
Valley by early Sunday/D5. A midlevel jet streak of 80-100 kt will
translate from northern TX on Saturday/D4 toward the north-central
Gulf Coast by 12Z Sunday, with associated height falls. This wave
and associated jet max will then pivot east toward the Carolinas
during the day on Sunday/D5 before moving offshore, as an upper low
deepens over PA into Monday/D6.
The primary factor influencing severe potential with this system
will be boundary-layer moisture quality. Models such as the ECMWF
(which has good run-to-run consistency) continue to show only a
narrow plume of 50s to lower 60s F dewpoints ahead of a rapidly
moving cold front. This front and surface low will move across LA
and southern MS during the day on Saturday/D4, reaching western GA
and the FL Panhandle by 12Z Sunday. Mid-60s F dewpoints may
eventually reach the FL Straits late Sunday/D5, just prior to the
cold front moving across FL.
Forecast soundings reveal very little MUCAPE present ahead of the
cold front over the weekend. Further, low-level lapse rates are
forecast to be so poor as to not even favor a strongly
forced/low-CAPE severe event, despite the strong shear. This is due
to the antecedent surface ridge over the Southeast, with
insufficient time to warm prior to the next front.
Since the only limiting factor will be instability, subsequent model
runs will be monitored closely for either 1) A slowing of the upper
trough (which would allow more time for airmass recovery), or 2) A
faster return of mid/upper 60s F dewpoints which may lead to
sufficient SBCAPE.
As such, potential is currently too low for a 15% or greater severe
probability during the Saturday/D4 through Sunday/D5 period. As the
event nears in time, lower severe probabilities may still be added,
should the parameters remain as currently forecast.
Beyond Sunday/D5, it appears a stable air mass will remain over much
of the East due to high pressure, with only gradual dewpoint
recovery across the Gulf of Mexico as the flow regime aloft becomes
more zonal.
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