Mesoscale Discussion 2149
Issued: · Valid: –
Summary
Thunderstorms moving southeastward through the Black Hills into northwestern and west-central Nebraska this evening may produce large hail and severe wind gusts.
Product Text
000 ACUS11 KWNS 271843 SWOMCD SPC MCD 271843 NEZ000-SDZ000-272045- Mesoscale Discussion 2149 NWS Storm Prediction Center Norman OK 0143 PM CDT Thu Aug 27 2026 Areas affected...portions of the Black Hills into northwestern and west-central Nebraska Concerning...Severe potential...Watch likely Valid 271843Z - 272045Z Probability of Watch Issuance...80 percent SUMMARY...Thunderstorms forming on the Black Hills will evolve southeastward through the evening, bringing a risk for large to very large hail and severe wind gusts. DISCUSSION...Latest surface analysis depicts a corridor of low-60s F dewpoints across northwestern Nebraska and southwestern South Dakota that have been maintained by moist southerly/southeasterly low-level flow. Combined with strong diurnal heating and weak ascent associated with a subtle mid-level wave progressing southeastward out of eastern Montana, convective initiation is likely across the Black Hills within the next 1-2 hours. Supercells will be the initial storm mode owing to strong northwesterly flow aloft and 40-45 kts of effective shear. While some uncertainty remains regarding convective evolution (particularly supercell longevity and the potential for eventual upscale growth), very steep mid-level lapse rates and elongated hodographs sampled by the 18z UNR observed sounding will support a risk for large to very large hail (up to 2-3+ inches in diameter) with any sustained supercells. Severe to perhaps significant severe wind gusts of 65-75 mph may also occur with these supercells, with a greater threat for severe gusts likely to accompany any convective cluster that eventually evolves as this activity progresses southeastward. Regardless of the exact storm mode evolution, a Severe Thunderstorm Watch will likely be needed once convective development currently noted over the Black Hills matures. ..Chalmers/Mosier.. 08/27/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LBF...UNR...CYS... LAT...LON 44280348 43540157 43030059 42710030 42330028 41850058 41500113 41320192 41520251 42000294 43020345 44050394 44310382 44280348 MOST PROBABLE PEAK WIND GUST...65-80 MPH MOST PROBABLE PEAK HAIL SIZE...2.00-3.50 IN