SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0647 AM CST Fri Jan 26 2024
Valid 261300Z - 271200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Isolated strong thunderstorms are possible this afternoon over parts
of west Texas, and tonight near the central Gulf Coast and over
Louisiana. Organized severe weather appears improbable.
...Synopsis...
The mid/upper-level pattern will remain progressive over the CONUS
this period, with a trough now over CO and NM being the main
convective influence aloft. This perturbation will house an
intermittently closed 500-mb low -- initially over east-central/
northeastern NM. That low should move roughly eastward across the
southern High Plains today, reaching the Caprock Escarpment between
LBB-CDS around 00Z, then moving roughly down the Red River Valley to
near I-35 in southern OK or extreme north-central TX by 12Z
tomorrow. By that time, the positively tilted trough should extend
from there southwestward to northern Coahuila.
At the surface, a broad, wavy baroclinic zone was analyzed across
the northern Gulf, modulated on the mesoscale by convective
boundaries. This feature should shift north but still remain mostly
offshore through the period, except for some warm-frontal incursion
into the MS/AL/western FL Panhandle region possible near the end of
the period. This would occur southeast of frontal-wave low
development over the northwest Gulf, offshore from the TX Coast, in
response to the approaching mid/upper trough. The low should move
northeastward close to a LCH-JAN track overnight, with a synoptic
warm front/inverted trough northeastward into the southern
Appalachians.
...West TX...
An organized thunderstorm or two may move southeastward across the
southern South Plains and/or northern Permian Basin regions of west
TX this afternoon, with potential for strong gusts and/or hail
approaching severe limits. Though surface temperatures will remain
cool over this region today (50s to low 60s in general), cooling
aloft with the approaching trough will steepen low/middle-level
lapse rates enough to support isolated strong convection, amid
30-40-kt effective-shear magnitudes. Inflow-layer parcels may even
become briefly surface-based, depending on cloud breaks and
insolation duration locally, with MLCAPE in the 300-700 J/kg range
possible along the southern rim of the cold-core region. Lack of
more-substantial inflow-layer moisture/buoyancy should preclude an
organized/areal severe threat.
...Gulf Coast States...
Strong convection is evident over open Gulf waters south of LA, in
IR satellite pictures, lightning data and imagery from distantly
located radar(s), with an extensive area of downstream anvil
material and precip from that also being shown in radar composites.
This precip may be under-depicted in composites, given the
unavailability of the closest (former Slidell) radar while it is
being relocated westward. This convection, being surface-based over
a well-modified and relatively high-theta-e boundary layer, is
likely to remain both organized and over the Gulf through the day
and into much of tonight. Meanwhile, a relatively stable boundary
layer to its north should be maintained and reinforced by:
1. Its own continuing downshear precip plume, and
2. Additional, widely scattered to scattered thunderstorms expected
to form over east TX and LA from this afternoon through tonight, as
elevated warm advection and moisture transport occur beneath
steepening midlevel lapse rates overnight.
Any sustained/discrete convection overnight in LA may produce hail
with MUCAPE up to about 1500 J/kg and 40-50-kt effective-shear
magnitude possible. However, with a lack of elevated MUCINH
reasonably apparent in forecast soundings, storm mode may become
clustered/messy fairly quickly. For now any severe-hail threat
appears too conditional/isolated for probabilities. One area of
interest for the last few hours of the period may be the coastal
corridor around BIX-MOB-PNS, where theta-e advection may render
surface-based parcels if earlier convection and related boundaries
move away long enough beforehand. For now the predictability of
such mesoscale processes remains too low to introduce unconditional
severe probabilities, but this potential will be monitored through
remaining outlook cycles.
..Edwards/Gleason.. 01/26/2024
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