ACUS01 KWNS 171256
SWODY1
SPC AC 171255

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0655 AM CST Tue Dec 17 2024

Valid 171300Z - 181200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE RED RIVER REGION INTO WESTERN TENNESSEE...

...SUMMARY...
Isolated severe thunderstorms are possible tonight through early
morning Wednesday across parts of the Red River region into western Tennessee.

...Synopsis...
In mid/upper levels, nearly zonal flow was evident over the CONUS
from coast to coast, perturbed by several minor shortwaves.  One of
these, however, will amplify through the period and influence
convective potential:  a trough now apparent in moisture-channel
imagery over the interior Pacific Northwest.  This feature will dig
southeastward today and begin to phase with a lesser trough now over
southeastern MT and eastern WY.  The combined trough should reach
western MN, eastern SD, central NE, and central/western CO by 00Z.
By 12Z, the trough should strengthen further, and extend near a line
from DBQ-IRK-TUL-CDS.

At 11Z, an outflow boundary was drawn from northwestern GA across
central parts of AL/MS to northeastern LA and near TXK, where it
intersected a slow-moving, weakening, cold to quasistationary front
drawn near a CRW-CSV-HSV-ELD-CRS line.  Farther north, frontogenesis
and cyclogenesis will occur today over the central Plains, as the
amplifying mid/upper trough approaches.  By 00Z, a frontal-wave low
should be located near TOP, with cold front southwestward across
south-central KS, northwestern OK, the TX Panhandle, and
northeastern NM.  The low should move past PAH into western KY by
12Z, with cold front over eastern to southwestern AR, central to
southwest TX, and the TX Big Bend region.  The outflow boundary and
residual front are expected to move slowly northward over the
Arklatex and Mid-South regions through late evening, before being
overtaken by the cold front.

...Red River region to Mid-South...
Isolated to widely scattered thunderstorms may develop on either
side of the northward-moving, slowly modifying outflow boundary from
this afternoon into this evening.  As the cold front intercepts that
boundary, scattered thunderstorms should form tonight along the cold
front.  A marginal threat for all severe hazards exists, mainly
overnight.

As the pre-cold-frontal boundaries shift northward, a relatively
undisturbed warm-sector airmass will spread over most of the outlook
area before the cold front arrives late tonight.  The strongest
DCVA/cooling aloft and steep midlevel lapse rates related to the
approaching trough will remain behind the cold front.  However, a
tightening height gradient, related strengthening deep shear, and
large-scale lift within an intensifying LLJ/WAA plume will spread
across the warm sector this evening and overnight.  These processes
will destabilize, moisten and increase shear in low levels.  Surface
dewpoints generally in the 60s F (greater southwestward) will
contribute to MLCAPE near 1000 J/kg from the Arklatex into at least
southwestern TN, diminishing northeastward from there.  A shallow,
neutral to stable near-surface thermal profile will be present
nocturnally, but may not preclude strong gusts or a tornado.
Substantially front-parallel flow aloft will lead to a dominant
quasi-linear mode with the frontal activity, but the marginal
hail/tornado threat should exist with any antecedent, persistent,
relatively discrete cells.  Embedded LEWP/bowing configurations in
the frontal band will pose the greatest local gust potential.

..Edwards/Goss.. 12/17/2024

$$
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