US Mesoscale Discussions

Storm Prediction Center Mesoscale Discussion 890

   Mesoscale Discussion 0890
   NWS Storm Prediction Center Norman OK
   1126 AM CDT Wed May 22 2024

   Areas affected...Northeast AR...Western and Middle TN...Northwest
   MS... Far Southwest KY

   Concerning...Severe potential...Watch likely 

   Valid 221626Z - 221830Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Increasing thunderstorm coverage is anticipated from
   northeast Arkansas into western and middle Tennessee, northwest
   Mississippi, and far southwest Kentucky this afternoon. Large hail
   and strong gusts are possible, and a watch will likely be needed

   DISCUSSION...Recent radar imagery has shown and increase in deeper
   convection across northeast AR, along and ahead of a
   southeastward-progressing cold front. Airmass preceding this front
   continues to destabilize, with recent surface observations sampling
   temperatures in the low 80s and dewpoints in the upper 60s/low 70s.
   This warm and moist low-level environment is helping to support
   strong buoyancy, despite relatively warm mid-levels and associated
   poor lapse rates. Recent mesoanalysis estimates MLCAPE is ranges
   from around 2500 J/kg across northeast AR to around 1000 J/kg over
   middle TN. Deep layer vertical shear over much of this region is
   currently modest, with mesoanalysis estimating effective bulk shear
   around 30 to 40 kt. Both buoyancy and vertical shear are forecast to
   increase throughout the afternoon, with the increase in buoyancy
   driven by continued heating and the increase in shear supported by
   increasing mid-level flow. 

   General expectation is for the currently shallow convection ahead of
   the front to deepen over time, with thunderstorm development likely.
   Increasing deep layer shear should promote an organized storm mode,
   with supercells possible. Large hail up to 1.75" to 2" in diameter
   will likely be the primary risk with initial, more cellular storms.
   The ongoing activity over northwest AR is expected to continue
   eastward, with some interaction between this activity and the more
   cellular, pre-frontal development is anticipated. This interaction,
   coupled with the steady southeastward progression of the cold front,
   will likely promote the transition to a more linear mode. Given the
   strengthening westerly flow aloft and ample low-level moisture, the
   development of a forward-propagating MCS is possible. Damaging gusts
   would be the primary risk with any linear development.

   Given all of these factors, a watch will likely be needed soon to
   cover the severe potential.

   ..Mosier/Hart.. 05/22/2024

   ...Please see for graphic product...


   LAT...LON   35109187 36548997 36878848 36278737 34918840 34178997
               34219091 35109187 

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