SPC AC 231226

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0726 AM CDT Tue Apr 23 2024

   Valid 231300Z - 241200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS
   AFTERNOON/EVENING ACROSS NORTHWEST TX...

   ...SUMMARY...
   Isolated severe thunderstorms capable of producing large hail (2+
   inch diameter) and gusts to 65 mph will be possible this afternoon
   and evening across northwest Texas. Additional strong storms
   producing hail up to 1 inch diameter and gusts up to 60 mph are
   possible from southeast Wisconsin and northern Illinois into Lower
   Michigan.

   ...Northwest TX area this afternoon/evening...
   No appreciable changes to the prior outlook.  In the wake of a
   midlevel trough crossing the Great Lakes, a surface cold front will
   move southward across KS/OK today, eventually stalling by tonight
   across southeast OK and northwest TX.  There will be sufficient
   cross-Rockies flow aloft for lee cyclogenesis across eastern NM and
   adjacent west central TX, which will maintain southerly low-level
   flow and northward advection of a modifying western Gulf air mass
   into the frontal zone by mid-late afternoon.  Strong surface heating
   along the west edge of the returning moisture will result in a
   sharpening dryline by late afternoon, with a dryline/front triple
   point likely just off the Caprock.  Isolated thunderstorm
   development will be most probable near the triple point after 21z,
   and convection will subsequently move southeastward before weakening
   by late evening.  The storm environment will be characterized by
   moderate buoyancy (MLCAPE of 1500-2000 J/kg), steep midlevel lapse
   rates near 9 C/km, and sufficient deep-layer shear for supercells. 
   Isolated very large hail of 2-2.5 inches in diameter will be the
   main threat, along with a few 55-65 mph outflow gusts.

   ...Northern IL/southeast WI/Lower MI late this afternoon/evening...
   Only minor changes to the MRGL risk area in lower MI.  A midlevel
   trough over the upper MS Valley this morning will continue
   east-southeastward over the Great Lakes by Wednesday morning.  An
   associated surface trough will likewise move southeastward, and this
   trough will be preceded by a band of rain with minimal buoyancy. 
   Behind the rain band, surface heating with steepening low-level
   lapse rates and cooling midlevel temperatures will support weak
   surface-based buoyancy just ahead of a secondary frontal surge. 
   Some low-topped convection will be possible in this zone late this
   afternoon through late evening from northern IL/southeast WI into
   lower MI.  The storms could pose a marginal hail/wind threat.

   ..Thompson/Kerr.. 04/23/2024

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