213
ACUS01 KWNS 051952
SWODY1
SPC AC 051951

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0251 PM CDT Sun May 05 2024

Valid 052000Z - 061200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTH TEXAS
INTO THE MIDDLE TEXAS COASTAL PLAIN...

...SUMMARY...
Scattered severe thunderstorms are possible across parts of
south-central Texas eastward into parts of southeast Texas, mainly
this afternoon and early evening.

...20Z Update...
Primary change with this update was to increase severe probabilities
across the Arklatex region.

..Arklatex..
Low-level moisture continues to quickly advect northward into the
region, with a resulting increase in buoyancy as well. Recent
surface analysis places a weak low over far southeast OK, with
modest troughing extending southwestward from this low. An effective
warm front also extends southeastward from this low, coincident with
the leading edge of the better low-level moisture. Interaction of
these surface features with the destabilizing airmass could result
in thunderstorm development. Vertical shear is strong enough to
support organized storm structures, and a few storms may be able to
produce hail and/or damaging as well as a brief tornado.

...Elsewhere...
Forecast outlined in the previous outlook (appended below) remains
valid for South TX, where supercells capable of large to very large
hail and damaging gusts are ongoing. These will likely continue for
the next few hours while slowly progressing southward.

Also, as discussed in the previous outlook and recently issued MD
#640, the potential for isolated damaging gust will persist across
the Upper OH Valley into the early evening.

..Mosier.. 05/05/2024

.PREV DISCUSSION... /ISSUED 1129 AM CDT Sun May 05 2024/

...South TX to Mid-South/lower Mississippi Valley...
An ongoing linear sub-severe MCS over AR moving north-northeast will
likely continue into portions of northeast AR/southeast MO and
adjacent parts of KY/TN through mid afternoon.  Some additional
heating may lead to some invigoration of storms along the leading
edge of outflow with a localized strong/severe risk.  Farther
southwest across south-central into southeast TX, an earlier MCV
over western LA and convective overturning from overnight
thunderstorm activity has left a remnant outflow boundary draped
across southeast TX.  South of the boundary, a very moisture-rich
airmass (16 g/kg lowest 100mb mean mixing ratios) beneath a residual
plume of steep 700-500 mb lapse rates, are contributing to moderate
to strong buoyancy.

Water-vapor imagery shows a mid- to upper-level impulse moving east
over northern Mexico and into south-central TX late this morning.
Recent thunderstorm development over south-central TX to the middle
TX coast may be in part due to ascent related to this upper feature.
Isolated to scattered thunderstorms will probably continue to
intensify with severe multicells or supercells with large hail,
damaging gusts and at least marginal tornado potential this
afternoon.  In the absence of notable mid/upper support behind the
shortwave trough, convection may diminish rapidly through the
evening, as the boundary layer stabilizes from both nocturnal
cooling and spreading outflow air.

...Upper Ohio Valley vicinity...
As a mid-level trough glances the region to the north over mainly
southeast Canada, a surface front will provide a focus for lift and
thunderstorm development this afternoon.  A plume of richer
low-level moisture, characterized by lower 60s deg F surface
dewpoints, is located ahead of the cold front and west of a
north-south oriented warm front over western PA.  Continued heating
will result in moderate buoyancy and favor the development of
scattered thunderstorms.  Modest low to mid-level flow will limit
overall storm intensity, but some multicellular organization is
possible.  Isolated hail/damaging gusts will be the primary hazards
with the stronger storms before this activity weakens by early
evening.

$$