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.

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