SPC AC 201952

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0252 PM CDT Tue May 20 2025

   Valid 202000Z - 211200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
   THE MID MS VALLEY TO THE CENTRAL APPALACHIANS...

   ...SUMMARY...
   Multiple rounds of severe thunderstorms are expected today through
   this evening, centered on the Mid/Deep South, Tennessee/Lower Ohio
   Valleys, and Cumberland Plateau. Tornadoes, some of which could be
   strong, along with scattered to widespread damaging winds, and large
   to isolated significant severe hail will be possible.

   ...20Z Update...
   Much of the previous forecast remains on track. Earlier storms
   across the TN Valley have matured into a QLCS, which is now
   approaching the central Appalachians. These storms should progress
   toward the eastern extent of a buoyant warm sector with a continued
   risk of damaging gusts and perhaps a couple of tornadoes. Storms
   poised to cross the MS River over the central MS Valley, and more
   discrete storms farther east over western TN/northern MS, should
   intensify further as they move eastward amid a strongly sheared and
   unstable airmass. The more intense, discrete storms will be capable
   of large to very large hail and at least isolated tornadoes. The
   more dominant supercells that move into northeast MS, middle TN, and
   southern KY, where surface is flow is relatively more backed, will
   have the best chance at producing a strong tornado. Lastly, storms
   should continue to intensify ahead of a surface low over central IL
   and immediate surrounding areas. Shear/buoyancy over this region
   favors supercell structures with a continued large hail/tornado
   risk.

   ..Squitieri.. 05/20/2025

   .PREV DISCUSSION... /ISSUED 1115 AM CDT Tue May 20 2025/

   ...KY/TN...
   Thunderstorms are ongoing across central KY/middle TN.  These storms
   will progress eastward through the afternoon into a moist and
   increasingly unstable air mass over eastern KY/TN and eventually
   into western WV/VA.  Most model guidance suggests that storms will
   intensify through the day, with an increasing risk of damaging wind
   gusts and a few tornadoes.  Refer to MCD #902 for further details.

   ...AR into the TN Valley this afternoon/evening...
   In the wake of the aforementioned convection, rapid heating is
   occurring across eastern AR/west TN/northern MS.  Surface dewpoints
   in the upper 60s to 70s and steep mid level lapse rates will yield
   afternoon MLCAPE values around 3000 J/kg and only a weak cap.  This
   will lead to the development of multiple clusters of intense
   thunderstorms (including supercells) that will track eastward
   through the afternoon and evening hours.  The initial storms will
   pose a risk of very large hail and a few tornadoes.  As the activity
   progresses eastward, the risk of damaging winds will increase with a
   persistent risk of tornadoes.  Strong tornadoes will be possible. 
   Storms are expected to get as far east as northwest GA tonight
   before slowly weakening.

   ...MO/IL...
   Satellite imagery shows a well-defined shortwave trough and
   associated surface low over IA/MO.  Ahead of this feature, southerly
   low-level winds have transported mid 60s dewpoints into central IL,
   where strong heating is now occurring.  This will result in moderate
   CAPE across the region and encourage rapid thunderstorm development
   over northeast and east-central MO by mid-afternoon.  Steep lapse
   rates aloft and favorable deep-layer shear will support supercell
   structures capable of large hail, damaging winds, and a few
   tornadoes.  Storms will track across IL and into central IN this
   evening.

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