FXUS65 KMSO 221027 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 427 AM MDT Fri May 22 2026 .DISCUSSION... KEY MESSAGES: - Warming and drying trend expected through the weekend. - Showers and thunderstorms on Monday with cold front moving through by Tuesday. - Tuesday could be quite the wet day as a large upper low becomes situated to our southwest. There's a 50 to 70% probability for widespread rainfall amounts exceeding 0.25" by Wednesday morning. - Upper low keeps unsettled weather going next week, so keep that rain gear handy! Scattered showers are possible this afternoon and evening across northwest Montana and along the Divide. Impacts will remain limited to brief, localized rainfall and wind gusts up to 30 mph. However, sufficient instability may trigger an isolated thunderstorm within Glacier National Park. This Weekend/Water Safety: A significant warming trend will bring summer-like temperatures to the region by the weekend. With the warm air temperatures, outdoor recreation will likely increase around area lakes and rivers. Please be aware that local waterways continue to run extremely cold due to ongoing mountain snowmelt. Plunging into cold water without acclimatization can induce cold water shock, which drastically alters breathing, heart rate, and blood pressure, creating life- threatening conditions. Always wear a life jacket to stay afloat and exercise caution. For more information on cold water hazards, visit weather.gov/safety/coldwater. Ensemble weather models have surprisingly become more inline with each other for Monday's weather. A large upper level low will drop south and east over the Pacific Northwest by Monday. This places us in southwest to southerly flow aloft which is a good map-type for showers and thunderstorms. Instability is marginal which could support gusty winds, lightning and small hail. As the flow turns more southerly later Monday, that will provide a lot of cloud cover, thereby limiting instability a bit. By Monday night,as the cold front makes its way into western Montana, the wrap-around moisture begins to kick in. All the ensemble clusters show our region under general rising motion as the upper level low wobbles and meanders over Oregon, Idaho and Nevada through Tuesday night. This is the period that the National Blend of Models has the highest probabilities for widespread rainfall. The probabilities show 50 to 70 percent of exceeding 0.25", 48 hours ending Wednesday morning. As such, Tuesday could be the coolest day of the week for some with highs ranging from the 50s to 60s, 5 to 10 degrees cooler than average. As the cutoff meanders to out south and west, there is the potential for Gulf moisture to get advected northwards over the Plains into the Montana region by Wednesday and Thursday. Ensembles show +2 to +3 standard deviations or 150+ percent of normal moisture(Precipitable Water). With that kind of almost "humid" air for our region, could result in heavy rain-producing showers or thunderstorms. By Thursday, the ensemble clusters depict some eastward movement with the mean solution putting the upper low over northern Nevada. By Friday the ensemble means all show this low starting to move a little faster, the ECMWF has it ejecting towards the Yellowstone region while the GFS ensemble is further south. && .AVIATION...Sufficient instability may support an isolated thunderstorm near Glacier National Park this afternoon. Expect localized wind gusts of 20-25 knots near any thunderstorm or stronger shower activity which impact KGPI. Otherwise, light and diurnally driven winds will continue at all terminal sites. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$