376 ACUS11 KWNS 231920 SWOMCD SPC MCD 231919 MTZ000-WYZ000-IDZ000-232115- Mesoscale Discussion 2099 NWS Storm Prediction Center Norman OK 0219 PM CDT Sun Aug 23 2026 Areas affected...Central Montana and adjacent portions of Idaho and northwest Wyoming Concerning...Severe potential...Watch possible Valid 231919Z - 232115Z Probability of Watch Issuance...60 percent SUMMARY...Thunderstorm development is expected in the coming hours within the northern Rockies. This activity will likely intensify as it spreads east across central Montana and portions of northwest Wyoming. Watch issuance is probable over portions of the region given the downstream convective environment. DISCUSSION...Growing cumulus is evident in latest GOES imagery within the higher terrain of northwest WY and eastern ID/western MT due to a combination of daytime heating and increasing ascent (both orographic and dynamic lift ahead of an approaching upper wave). Regional VWPs are also depicting increasing mid-level flow associated with the approach of the upper wave, resulting in gradual elongation of hodographs across the region. Concurrently, temperatures downstream across central MT are warming into the mid to upper 80s, which appears sufficient to erode lingering inhibition and support around 500-1000 J/kg MLCAPE based on modifications to forecast soundings. Consequently, it appears likely that thunderstorm development will occur in the coming hours as ascent continues to spread east over the destabilizing air mass. Recent guidance supports this notion and depicts initially discrete/semi-discrete cells across the region. This early activity will likely pose a threat for large hail (most likely 1 to 1.75 inch in diameter) given adequate hodograph elongation. With time, clustering and upscale growth should support an increasing wind threat across central MT through the late afternoon and evening hours. Based on the downstream environment and recent high-res guidance output, wind speeds up to 60-80 mph appear possible with the more intense/organized clusters. Watch issuance is probable in the next 1-2 hours as thunderstorms begin to develop and mature. ..Moore/Smith.. 08/23/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BYZ...GGW...RIW...TFX...PIH... LAT...LON 43580985 43721101 43891184 44241224 44671230 45951204 46121196 47331187 48601189 49021155 49060898 48330862 47280851 46360853 45420852 44250862 43730882 43580908 43580985 MOST PROBABLE PEAK WIND GUST...65-80 MPH MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN  541 ACUS11 KWNS 231924 SWOMCD SPC MCD 231924 NEZ000-SDZ000-NDZ000-232130- Mesoscale Discussion 2100 NWS Storm Prediction Center Norman OK 0224 PM CDT Sun Aug 23 2026 Areas affected...southeast North Dakota...western South Dakota...and portions of the Nebraska Panhandle Concerning...Severe potential...Watch possible Valid 231924Z - 232130Z Probability of Watch Issuance...60 percent SUMMARY...The threat for severe storms capable of large hail up to two inches and severe wind gusts up to 75 mph is expected to increase by mid to late afternoon. A severe thunderstorm watch is possible. DISCUSSION...Visible satellite and lightning data indicate incipient thunderstorm development over the Black Hills, which is being aided by heating along the high terrain and convergence in the vicinity of a surface low. The 18Z Rapid City sounding is likely representative of the ambient environment, featuring modestly steep mid-level lapse rates atop a moist boundary layer with MLCAPE of 1500-2000 J/kg and some residual capping. While deep-layer shear isn't particularly strong, the 18Z Riverton, WY sounding sampled stronger winds above 5-6 km AGL, which will spread east into the region later this afternoon. Elsewhere, high-based convection is developing over portions of southeast WY into the western NE Panhandle amidst a deeper, well-mixed boundary. Deepening cumulus is also being observed over far eastern MT, along and ahead of a weak surface trough. Latest time-lagged HRRR and RRFS ensemble guidance indicates the potential for widely scattered storms to evolve by mid to late afternoon from parts of the western Dakotas into the NE Panhandle, which seems reasonable based on the observational signals mentioned above. Parameter space appears supportive of organized storm modes, including supercells capable of large hail, potentially up to two inches in diameter. Severe wind gusts up to 75 mph also appear possible, especially with the storms moving into the NE Panhandle. Convective trends are being monitored for a possible severe thunderstorm watch. ..Mead/Smith.. 08/23/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BIS...LBF...UNR...CYS... LAT...LON 44000392 44660399 47280403 47290368 47130326 44500268 42180209 41680239 41640291 42540322 43690382 44000392 MOST PROBABLE PEAK WIND GUST...65-80 MPH MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN