SPC 1300Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0702 AM CST Tue Nov 24 2020

Valid 241300Z - 251200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
SOUTHERN PLAINS INCLUDING OKLAHOMA...TEXAS PANHANDLE...AND FAR
SOUTHERN KANSAS...

...SUMMARY...
Severe thunderstorms are possible from mid/late afternoon into
tonight across portions of northern Texas, Oklahoma, and southern
Kansas to the Ozarks, Mid-South, and Ark-La-Tex regions. Large hail
and severe wind gusts are the primary hazards.

...Central/Southern Plains to Ozarks...
A shortwave trough centered over the Four Corners area early this
morning will eject east-northeastward today and reach the Ozarks
tonight, with a 90+ kt polar jet overspreading Oklahoma/northern
Texas toward the Ozarks as the system takes on an increasingly
negative tilt. Surface cyclogenesis will initially occur across the
south-central High Plains today, with middle/upper 50s F surface
dewpoints developing northward into far eastern Texas Panhandle and
western Oklahoma by late afternoon. 

As intense height falls/forcing for ascent arrive into the region,
initial near-surface-based storm development/intensification should
occur within the immediate post-surface-frontal regime across the
Oklahoma/northern Texas Panhandles by around mid-afternoon, with
this convection developing east-northeastward and intensifying
toward the triple point vicinity into northwest Oklahoma through
early evening. Despite modest boundary layer moisture, relatively
cool mid-level thermal profiles and steep lapse rates will support
adequate instability for severe-caliber storms in the presence of
very strong vertical shear. A few initial supercells capable of
large hail are expected, along with some tornado risk particularly
across northwest/west-central Oklahoma. Upscale growth into bands
should otherwise occur during the evening with an increasing
potential for damaging winds as storms race east-northeastward
across northern Oklahoma and far southern Kansas. 

...ArkLaTex/Mid-South/Lower Mississippi Valley...
Farther south-southeast, a somewhat separate corridor of at least
isolated severe thunderstorm development could occur across
northeast Texas, southern Arkansas, and northern Louisiana roughly
from mid-evening into the overnight. As the warm front moves
north-northeastward across the region tonight, guidance such as the
NAM/RAP suggest a weakening trend of convective inhibition
nocturnally in conjunction with an increasing prevalence of low/mid
60s F surface dewpoints. While uncertainties remain regarding the
magnitude of the severe risk across this region, a late-night
through early morning damaging wind/tornado risk cannot be
discounted. Observational/short-term guidance trends will be
reevaluated today for a possible categorical Slight Risk
upgrade/regional expansion.

..Guyer/Broyles.. 11/24/2020

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