Storm Prediction Center Mesoscale Discussion 915

   Mesoscale Discussion 0915
   NWS Storm Prediction Center Norman OK
   0814 PM CDT Tue May 20 2025

   Areas affected...Southern Appalachians

   Concerning...Tornado Watch 305...308...

   Valid 210114Z - 210315Z

   The severe weather threat for Tornado Watch 305, 308 continues.

   SUMMARY...A tornado, wind-damage and large-hail threat will continue
   across parts of the southern Appalachians over the next few hours. A
   strong tornado will be possible.

   DISCUSSION...The latest mosaic radar imagery shows a mix of
   supercells and short-line segments ongoing from east-central
   Tennessee southward into northern Alabama. The airmass ahead of this
   convection is unstable, with the RAP showing SBCAPE in the 1000 to
   2000 J/kg range. The instability, along with large-scale ascent
   associated with a shortwave trough moving through the Ohio and
   Tennessee Valleys, will maintain a severe threat with the stronger
   cells. The latest WSR-88D VWP at Morristown, TN has 0-6 km shear
   near 55 knots, and 0-3 km storm-relative helicity around 200 m2/s2.
   This will be favorable for supercells. The more dominant supercells
   could have a tornado threat, and potential for wind damage and large
   hail. The wind-damage threat could also be concentrated along and
   ahead of the more intense short-line segments. The severe threat may
   become more isolated with eastward extent, as instability gradually
   becomes weaker this evening.

   ..Broyles/Gleason.. 05/21/2025

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...GSP...MRX...JKL...FFC...OHX...BMX...HUN...

   LAT...LON   37438435 37018465 35638514 34958611 34658639 34518638
               34308631 34168608 34038537 34148434 35058373 36488305
               37238281 37648315 37708371 37438435 

   MOST PROBABLE PEAK TORNADO INTENSITY...120-150 MPH
   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN