SPC AC 231241

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0741 AM CDT Tue May 23 2023

   Valid 231300Z - 241200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS
   AFTERNOON/EVENING FROM THE SOUTH PLAINS INTO CENTRAL TX...

   ...SUMMARY...
   Isolated very large hail and damaging gusts will be possible this
   afternoon/evening from South Plains into central Texas.  Additional
   strong to severe thunderstorms will be possible across Florida and
   the northern Great Basin.

   ...South Plains into central TX this afternoon/evening...
   Overnight convection dissipated early this morning over central TX,
   with only subtle hints of lingering convective outflow.  The surface
   pattern today will consolidate into a loose baroclinic zone from
   northwest TX to the South Plains, southeast of a weak lee cyclone
   near the TX/NM border.  Aloft, a series of weak perturbations will
   crest the ridge over NM and move southeastward toward the TX
   Panhandle by this evening.  Surface heating and convergence/ascent
   along the baroclinic zone will support thunderstorm development by
   mid afternoon in a loose northwest-southeast band near the front,
   and storms will subsequently move southeastward through late
   evening.

   Midlevel lapse rates will be a little steeper today (near 8 C/km)
   compared to yesterday, and low-level moisture will be the same or
   slightly greater (58-64 F dewpoints).  MLCAPE is expected to reach
   2000-3000 J/kg by mid-late afternoon along the front with minimal
   convective inhibition.  Vertical shear will be sufficient for
   supercells given 25-30 kt midlevel westerly flow atop low-level
   east-southeasterly flow, with effective bulk shear of 30-40 kt and
   relatively straight hodographs.  The initial, more discrete
   supercells will be capable of producing isolated very large hail of
   2 to 3 inches in diameter, while the threat for damaging winds of
   60-75 mph will increase as convection grows upscale into one or more
   clusters.  Any tornado threat will rely on favorable storm
   interactions, and/or locally curved hodographs close to the front
   this evening, at the same time upscale growth into clusters is
   probable.

   ...FL this afternoon...
   Similar to yesterday, a weak midlevel trough persists over MS/AL/GA,
   with a diffuse surface front across north FL.  Surface heating will
   drive local sea breeze circulations south of the front, with storm
   formation expected from the FL Panhandle into the peninsula by
   early-mid afternoon.  Moderate buoyancy and effective bulk shear of
   25-30 kt will favor a mix of semi-organized multicells and some
   low-end supercells.  The strongest storms will be capable of
   producing isolated damaging downburst winds of 50-60 mph, while
   steeper lapse rates aloft (in the hail growth zone) compared to
   yesterday may support isolated, marginally severe hail.

   ...Northeast NV to southeast ID this afternoon/evening...
   A midlevel low will form over OR, and heights will rise over the
   northern Plains, allowing flow to back to south-southwesterly from
   NV into ID.  On the east edge of the stronger flow with the OR low,
   surface heating will result in steep low-level lapse rates and
   SBCAPE of 500-1000 J/kg this afternoon from northeast NV into
   southeast ID.  Scattered multicell clusters are expected in this
   zone, with the potential for isolated strong-severe outflow gusts of
   50-60 mph given the moderate buoyancy, effective bulk shear near 25
   kt, and inverted-V profiles with DCAPE approaching 1000 J/kg.

   ..Thompson/Broyles.. 05/23/2023

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