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