816
ACUS01 KWNS 041959
SWODY1
SPC AC 041958

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0258 PM CDT Sat May 04 2024

Valid 042000Z - 051200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR WEST
TEXAS...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
NORTHWEST/WEST-CENTRAL ILLINOIS...

...SUMMARY...
Scattered severe thunderstorms are expected across parts of the
southern High Plains into the Hill Country of central Texas this
afternoon and evening. Several storms may produce very large hail,
and a couple strong tornadoes are possible.

...20Z Update...

...Far West Texas into TX Hill Country/Central TX...
Outflow-augmented cold front continues to surge southward across the
Permian Basin. Development along the front has been relatively
short-lived thus far, primarily due to the undercutting of the
updrafts. Even so, buoyancy is building north of the front, so more
storm maturation and increasing severe potential appears possible
north of the front. A more thermodynamically favorable environment
exists south of the surging cold front, where there is a greater
potential for surface-based storms capable of all severe hazards,
including tornadoes.

This initially more discrete activity will likely increase in
coverage later this evening as the shortwave trough currently moving
through northern Mexico reaches Far West Texas. Some potential for
upscale growth exists as forcing increasing, with the resulting MCS
then pushing eastward through the Hill Country. Damaging wind gusts
will be the primary hazards with this convective line. However,
ample low-level moisture and veering low-level flow could support a
few line-embedded QLCS tornadoes.

...Western Illinois...
As mentioned in recently issued MCD #630, the airmass ahead of the
southeastward-progressing cold front will continue to destabilize as
dewpoints climb into the mid-60s and temperatures warm into the low
80s. Substantial instability (~1500-2000 J/kg MLCAPE) and modest
deep-layer shear will lead to some loosely organized multicell
thunderstorms capable of isolated hail and damaging gusts along and
ahead of the front later this afternoon.

..Mosier.. 05/04/2024

.PREV DISCUSSION... /ISSUED 1142 AM CDT Sat May 04 2024/

...TX/southern OK/extreme southeastern NM...
Not much change for this outlook update other than a minor southward
shift of severe probabilities across far southeast NM and West TX to
account for the projected cold front position by mid afternoon.
Still expecting widely scattered to scattered thunderstorms to form
this afternoon along and behind the cold front over west TX and
southeastern NM, as well as ahead of the cold front, near the
dryline and over strongly heated, relatively high elevations west of
the Pecos Valley.  The stronger updrafts will attain supercell
characteristics and pose a large-hail threat on both sides of the
front, with severe-wind and tornado potential more prevalent to its
south.  Forecast soundings south of the front indicate veering and
increasing flow with height which will become very favorable for
supercells.  It still appears one or two dominant, prefrontal,
mid/late-afternoon supercells may evolve and remain south of the
front.  The potential for a strong tornado in addition to giant hail
will be the primary hazards with these warm sector supercells.
Additional storm development is expected by early evening with an
amassing of cold pools eventually expected, as southeasterly 850mb
flow strengthens.  A severe MCS will likely evolve during the
evening and probably persist into the overnight as it moves east
across portions of the Edwards Plateau and central TX.  Have
expanded wind probabilities farther east to account for a lingering
threat for severe gusts and perhaps a localized risk for a tornado
late as this activity moves east of I-35.

...North/northeast TX to mid Mississippi Valley/western Great Lakes
vicinity...
A diurnal intensification of isolated to scattered thunderstorms is
expected this afternoon within this general corridor from the Red
River Valley northeastward into the IL/WI vicinity.  With much of
this region located in between larger-scale mid-level waves, modest
kinematic fields will tend to limit overall storm organization and
severe potential.  Nonetheless, heating of a moist boundary layer
will facilitate the development of moderate instability by early to
mid afternoon.  Mainly semi-organized bands of multicells and
clusters thereof will occasionally result in sporadic potential for
wind damage and large hail.  It appears perhaps a corridor for
greater wind damage potential may occur immediately ahead/downstream
of an MCV moving east across the mid MS Valley.  Model guidance
indicates slightly greater organized line segments and wind
potential later this afternoon from central into northern portions
of IL.  Have also expanded the MRGL northward into portions of WI
where sufficient destabilization will occur ahead of a front and
associated mid-level disturbance over the Upper Midwest.

$$