FXUS65 KMSO 110957 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 257 AM MST Tue Feb 11 2025 .DISCUSSION... KEY MESSAGES: - Dangerous cold in western Montana through Thursday morning. - Snow returns by Friday, with valley wintry mix, including the potential for freezing rain by Sunday. Surface and satellite infrared (IR) observations indicate bitterly cold temperatures this morning across western Montana. As of 2:30 AM MST, the coldest spot was Marias Pass, at -30F. Widespread temperatures of -20F or colder have also been reported along Highway 200, from Potomac to Lincoln. Stratus clouds have developed to the south and west of Missoula, which has reduced radiational cooling, resulting in milder temperatures in these areas compared to others. Cold weather advisories remain in effect across all of western Montana through this morning, due to the increased risk of hypothermia and frostbite. A weak shortwave trough will move southward from Alberta this afternoon, bringing an increase in stratus clouds. Upslope easterly flow along the divide will also lead to scattered snow showers. Forecast models suggest that the stratus clouds will persist into the evening and into Wednesday morning. This additional cloud cover will help prevent temperatures from falling as drastically as they did this morning, particularly in northwest Montana and along the divide. However, due to the ongoing cold air mass, low temperatures are still expected to drop below zero across western Montana and the high valleys of north- central Idaho. Looking ahead, the next weather system remains consistent across forecast models, with widespread light snow (greater than 60% probability) expected to arrive Thursday night into Friday. A broad low-pressure trough will move across the western U.S., bringing Pacific moisture within the southwesterly flow that will overrun the cold air trapped in the valleys, creating favorable conditions for widespread light snow. Guidance continues to suggest a reinforcing surge of Arctic air by Friday morning across northwest Montana and along the divide. Increasing north- northeast winds will also raise the risk of localized blowing and drifting snow. Ensemble model guidance indicates that another Pacific system will likely arrive by Sunday. A west-southwest flow pattern will bring moderating temperatures, along with the potential for mountain snow, especially along the Idaho-Montana border. Rising snow levels under warm air advection will increase the risk of mixed precipitation in the valleys, including freezing rain. Stay tuned for further updates! && .AVIATION... Widespread stratus clouds are visible in satellite imagery across north-central Idaho and along the US-93 corridor from Missoula southward to Salmon. Meanwhile, bitterly cold temperatures are being observed across northwest Montana and along the divide. Cold weather advisories remain in effect throughout the morning across western Montana, due to the risk of hypothermia and frostbite, especially for those planning to be outside for extended periods. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...Cold Weather Advisory until 1 PM MST Wednesday for Bitterroot/Sapphire Mountains...Butte/Blackfoot Region... Flathead/Mission Valleys...Kootenai/Cabinet Region...Lower Clark Fork Region...Missoula/Bitterroot Valleys... Potomac/Seeley Lake Region...West Glacier Region. ID...None. && $$