SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0659 AM CST Thu Jan 11 2024
Valid 111300Z - 121200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER THE
ARKLATEX REGION...
...SUMMARY...
Tornadoes, damaging to severe thunderstorm gusts and large hail are
possible tonight over the Arklatex region, and nearby parts of
southeastern Oklahoma, east Texas, Arkansas, and western/northern
Louisiana.
...Synopsis...
In mid/upper levels, broadly cyclonic flow will continue over most
of the CONUS this period. Within that, the principle influence will
be the southern portion of a shortwave trough -- evident in
moisture-channel imagery from WY southwestward across UT to the
southern Sierra. That southern lobe will dig southeastward across
AZ today, reaching central/southern NM, the ELP region, and northern
Chihuahua by 00Z. By 12Z tomorrow, this perturbation should become
negatively tilted, with an axis from north-central OK to east-
central TX. Mass response will be intense, with a compact, cyclonic
jet core of 150-160-kt at 250 mb and 110-130 kt at 500 mb by 12Z,
over a corridor from central TX to the Mid-South. By then, a 50-70-
kt LLJ should develop across parts of LA into the Mid-South region.
At the surface, 11Z analysis showed a low over southeastern WI, with
strong cold front southwestward over northern MO to central KS,
becoming quasistationary to warm across northwestern KS to another
low over northeastern CO. The northern low should move eastward and
weaken today, while strong cyclogenesis occurs with the southward/
southeastward-shifting CO low. By 00Z, the latter low should be
deepening over western OK, with the trailing Arctic cold front
surging southward across the southern High Plains, and a Pacific
cold front southwestward over far west TX. The fronts will merge
through the remainder of the period as the main cyclone elongates
along the front, while moving northeastward. By 12Z, the combined
cold front should extend from the low-pressure area over MO, across
western/central AR and east TX, to the northwestern Gulf shelf
waters. A dryline should develop today on the western rim of the
moist-advection plume, with the boundary extending from north-
central to deep south TX by 00Z. The dryline will be overtaken by
the cold front overnight, from north-south.
...Arklatex and vicinity...
Scattered thunderstorms are expected to develop by about 6Z over
portions of central/north-central TX near I-35, then shift eastward
and expand across much of the outlook area into early morning.
Activity should produce large hail early, some potentially
significant (2+ inches diameter), and pose an increasing threat for
damaging wind and at least a few tornadoes. Late tonight into early
morning, strong tornadoes may become possible with any supercells
crossing the Arklatex region as moisture, instability, lift, and
vertical shear all increase in tandem.
Large-scale ascent aloft will intensify tonight with the approach of
the mid/upper trough, spreading steepening midlevel lapse rates and
weakening CINH over the corridor of frontal forcing. From the early
development, the convective plume should grow northward as theta-e
increases ahead of the frontal segment farther inland, and southward
as the front overtakes more of the dryline and impinges on already
favorable moisture. Surface dewpoints in the upper 50s to mid 60s F
should spread into the Arklatex region just ahead of the front,
yielding a corridor of around 500-1000 J/kg MLCAPE, decreasing
northward into the Ozarks where return flow still is cool and not as
moist, and southward toward the coast where optimal lapse rates/
cooling aloft don't reach. Greater CINH with southward extent also
may impede any warm-sector deep-convective development tonight near
the coast, with potential increasing northward.
Kinematically, strengthening flow aloft not only will yield
favorable shear (e.g., 45-55 kt effective-shear vectors), but will
have a substantial component across the belt of strongest convective
lift associated with the front. This may aid potential for discrete
to semi-discrete supercell mode for at least a few hours, despite
rapidly intensifying deep-layer lift and quick growth in overall
convective coverage late tonight. Hodographs will be favorably
enlarged and shaped under the western rim of the strengthening LLJ,
with 200-400 J/kg effective SRH being common. In the lowest 1/2 to
1 km, SRH above 200 J/kg also is possible.
..Edwards/Jewell.. 01/11/2024
Read more
