ACUS03 KWNS 211928
SWODY3
SPC AC 211927
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0227 PM CDT Thu May 21 2026
Valid 231200Z - 241200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
CENTRAL AND SOUTH TEXAS TO THE MIDDLE TEXAS COAST AND IN THE
VICINITY OF THE RATON MESA INTO THE TEXAS AND OKLAHOMA PANHANDLES...
...SUMMARY...
Scattered strong to potentially severe storms appear possible across
portions of central and south Texas toward the middle Texas coast.
Isolated strong to severe storms are also possible from the Raton
Mesa vicinity into the Oklahoma and Texas Panhandles.
...Synopsis...
Broader-scale troughing will be maintained over the north-central
U.S. Saturday into Saturday night, with an embedded short-wave
trough moving through the central Plains. To the immediate east, a
short-wave trough initially over the OH Valley will lift northeast
through the Great Lakes. Meanwhile, a lower-latitude disturbance is
forecast to slowly track through TX. At the surface, an area of low
pressure will gradually undergo occlusion over OH into southwest
Ontario with a trailing front extending southwest through the lower
OH Valley into the southern Plains.
...Central and Southern Texas to the Middle Texas Coast...
There is general agreement in 12z model guidance that thunderstorms
will develop fairly early in the day across the Edwards Plateau,
east of a weak surface low and approaching short-wave trough. The
downstream air mass across central and southern TX is expected to be
moist with dewpoints in the 60s to low 70s, and within the eastern
fringe of a steep mid-level lapse rate plume, yielding moderate to
strong afternoon instability. As such, the early-day thunderstorms
are expected to increase in coverage and intensity through the
afternoon while advancing east/southeast into central and deep south
TX, and eventually toward the TX coast. Some enhancement of
deep-layer shear is forecast across south TX, which will aid in hail
production and cold pool organization, and resultant damaging wind
potential.
...Raton Mesa into the Oklahoma and Texas Panhandles...
Southeasterly, upslope flow will contribute to isolated thunderstorm development by mid to late afternoon along favored terrain. The
combination of a moderately unstable, steep-lapse-rate environment
and around 30 kt of deep-layer shear will support some potential for
supercell storm modes with an attendant risk for large hail. Storms
will tend to drift southeast into the OK and TX panhandles before
weakening.
...Southeast...
A moist and moderately unstable air mass is expected to develop
Saturday afternoon, with terrain and sea-breeze boundaries serving
as the main foci for diurnally enhanced thunderstorm development.
The models focus the most concentrated thunderstorm activity from
the Savannah River Valley into north FL. There is some model signal
for a weak mid-level disturbance and slightly stronger deep-layer
shear to potentially enhance that thunderstorm regime. Low wind
probabilities may eventually need to be added if confidence
increases in the existence of those features.
...Upper Ohio Valley...
A conditional risk of severe storms exists across the upper OH
Valley Saturday afternoon, east of the surface low and associated
surface front, where vertical shear will be enhanced. The main
uncertainty is the degree of instability within the narrow warm
sector, which varies considerably from model to model. Low
severe-weather probabilities may eventually be included, should
subsequent model trends indicate a more consistent signal for
stronger air mass destabilization.
..Mead.. 05/21/2026
$$
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