Mesoscale Discussion 1939
   NWS Storm Prediction Center Norman OK
   0223 AM CDT Sun Aug 18 2024

   Areas affected...South-Central SD...North-Central NE

   Concerning...Severe potential...Watch unlikely 

   Valid 180723Z - 181000Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Large hail is possible across south-central South Dakota
   and adjacent north-central Nebraska for the next few hours.

   DISCUSSION...Isolated thunderstorms have developed across
   south-central SD amid the warm-air advection regime fostered by the
   modest low-level jet over the central High Plains. Moderate to
   strong buoyancy (i.e. MUCAPE from 2000 to 3000 J/kg) is in place
   from southwest/south-central SD into central NE, with these storms
   developing near the maximum within this corridor. There is a sharp
   gradient in buoyancy with northeastward extent, with MUCAPE dropping
   from 3000 J/kg across southwest SD to less than 500 J/kg across
   eastern NE. This lack of buoyancy across eastern SD will likely
   limit storm development to the northeast of the ongoing storms until
   later this morning. The northwesterly deep-layer vertical shear
   suggests a southeasterly storm motion will be favored as updrafts
   mature. Large hail is possible with these storms for the next hour
   or two.

   Additional thunderstorm development appears possible to the
   southwest of the ongoing storms, fostered by a combination of
   warm-air advection and strengthening large-scale ascent attendant to
   a shortwave trough currently progressing northeastward through the
   central Rockies. The aforementioned corridor of moderate to strong
   buoyancy will support strong updrafts, with the moderate deep-layer
   vertical shear supporting updraft organization. Consequently, a few
   storms may become strong enough to produce large hail.

   ..Mosier/Smith.. 08/18/2024

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

   ATTN...WFO...FSD...ABR...GID...LBF...UNR...CYS...

   LAT...LON   44480225 44359977 42269836 41249980 41140134 43130293
               44480225