Storm Prediction Center Mesoscale Discussion 1999

   Mesoscale Discussion 1999
   NWS Storm Prediction Center Norman OK
   0203 PM CDT Sun Aug 16 2026

   Areas affected...portions of the Black Hills in southwestern South
   Dakota into far northern Nebraska

   Concerning...Severe potential...Watch unlikely 

   Valid 161903Z - 162100Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Isolated thunderstorms are forecast to evolve
   southeastward out of the Black Hills through this evening. The
   primary hazards will be isolated large hail and damaging wind gusts.

   DISCUSSION...Convective development is ongoing across portions the
   Black Hills in southwestern South Dakota and adjacent areas of
   Montana/Wyoming. Expectation is for at least an isolated
   thunderstorm or two to eventually evolve southeastward out of the
   Black Hills. While available buoyancy remains weak as of 1900 UTC,
   further insolation should result in additional destabilization
   through the afternoon to around 1000-1500 J/kg MLCAPE. Effective
   shear of 30-40 kts and steepening mid-level lapse rates may promote
   a supercell or two capable of isolated large hail, with steep
   low-level lapse rates and the possibility of eventual clustering
   also supporting a risk for occasional damaging/severe wind gusts.
   Current expectations are for thunderstorm/severe coverage to remain
   too isolated for watch issuance; however, a targeted Severe
   Thunderstorm Watch could be considered should convective
   coverage/severe risk trend greater than anticipated.

   ..Chalmers/Guyer.. 08/16/2026

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

   ATTN...WFO...LBF...UNR...

   LAT...LON   42840195 43010273 43410329 43900377 44210398 44500403
               44680385 44650321 44340258 43720168 43490148 43210137
               43050144 42890164 42840195 

   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN