ACUS11 KWNS 091901 SWOMCD SPC MCD 091901 SDZ000-092030- Mesoscale Discussion 1556 NWS Storm Prediction Center Norman OK 0201 PM CDT Thu Jul 09 2026 Areas affected...portions of the Black Hills and southwestern South Dakota Concerning...Severe potential...Watch unlikely Valid 091901Z - 092030Z Probability of Watch Issuance...20 percent SUMMARY...Isolated thunderstorms may move off the Black Hills in southwestern South Dakota and promote an isolated severe threat this afternoon. A further increase in strong to severe thunderstorm potential is expected late this afternoon and into the evening. DISCUSSION...An isolated thunderstorm has recently developed across the Black Hills in southwestern South Dakota. While latest objective analysis suggests that capping remains in place to the east of the Black Hills, modifying the nearby UNR 18z observed sounding for current surface observations suggests that inhibition is quickly eroding amid continued insolation. This may allow isolated convection to evolve eastward off of the Black Hills this afternoon. Should this scenario occur, storms would encounter increasing instability across central South Dakota, with modest effective shear (25-30 kts), well-mixed boundary layer profiles, and steep mid-level lapse rates (as sampled by the aforementioned UNR observed sounding) promoting a risk for isolated damaging/severe wind gusts and large hail. Given that this risk remains conditional on a storm persisting eastward off of the Black Hills, watch issuance is uncertain at this time. An increase in severe potential and convective coverage is then expected later this evening across portions of western South Dakota. ..Chalmers/Hart.. 07/09/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...UNR... LAT...LON 43410276 43380317 43430356 43580388 43830402 44130404 44500399 44700393 44790377 44790318 44750266 44550228 44200203 43840207 43580234 43410276 MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN