SPC AC 071636

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1136 AM CDT Tue May 07 2024

   Valid 071630Z - 081200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR
   INDIANA...WESTERN AND CENTRAL OHIO...AND NORTHERN KENTUCKY...

   ...SUMMARY...
   Scattered severe thunderstorms are expected across the southern
   Great Lakes and Ohio Valley this afternoon and evening.  A few
   tornadoes (some strong), large to very large hail, and
   severe/damaging winds all appear possible.

   ...Southern Great Lakes/Ohio Valley and vicinity...
   Considerable uncertainty remains for this forecast due largely in
   part to an ongoing broken squall line moving east across KY/IN/Lake
   Michigan and the related influences for airmass destabilization in
   its wake.  However, clearing skies in the MCS' wake will result in a
   seemingly sufficient period of heating during the afternoon. 
   Water-vapor imagery shows the deep-layer cyclone centered over the
   northern Great Plains.  A mid-level speed max rotating through the
   base of the larger-scale trough will move from the mid MS Valley
   late this morning into the southern Great Lakes by early evening. 
   Rapid strengthening of southwesterly 500-mb flow is forecast over
   northern IL into the northern half of IN through the mid-late
   afternoon.  As an effective warm frontal zone becomes draped across
   the southern Great Lakes/OH Valley regions, curved low-level
   hodographs beneath a lengthening of the mid and upper part of the
   hodograph will support a supercell risk.  It seems most probable
   based on morning model guidance that storms will initially develop
   across central/northern IL and move northeast into northern IN. 
   Isolated to scattered storms are forecast to eventually develop this
   afternoon across parts of the OH Valley in association with
   warm/moist-air advection---although considerable uncertainty remains
   regarding this scenario.  The stronger storms (i.e., supercells)
   will be potentially capable of a large to very large hail threat, in
   addition to several tornadoes (perhaps a few which may be strong).  

   ...Arklatex to north-central and south-central TX...
   Not much change in the forecast thinking across the Mid South
   southwestward into parts of TX.  Isolated severe thunderstorms are
   possible during mid/late afternoon.  Damaging gusts and large hail
   would be the main concerns.  The threat over the area is conditional
   -- more due to weak lift than thermodynamic considerations.  Surface
   dewpoints commonly in the 70s F will underlie a deep troposphere and
   enough middle-level lapse rates for MLCAPE in the 3500-4500 J/kg
   range.  Weak low-level winds will constrain hodograph size and
   boundary- layer shear.  However, enough mid/upper flow remains to
   support around 45-55 kt effective-shear magnitudes, yielding a
   conditional supercell environment.  In the absence of meaningful
   large-scale support, and with shallower overall lift near the
   front/dryline, convective coverage over this region is more in
   question and likely isolated.  Additional convection may form
   overnight in a warm-advection plume near and southeast of the front,
   across parts of the Mid-South to Arklatex regions.  Marginal hail
   and isolated damaging gusts would be the main concerns.

   ...Southeast KS late tonight...
   A strengthening LLJ and associated warm-air advection will be
   focused over the northeast OK/southeast KS region late tonight. 
   Forecast soundings show large MUCAPE amidst strong deep-layer shear.
   Large hail may accompany a stronger storm or two that manages to
   develop/become sustained during the 08-12z period.

   ..Smith/Jewell.. 05/07/2024

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