Area Forecast Discussion
Issued by NWS Missoula, MT
Issued by NWS Missoula, MT
826 FXUS65 KMSO 101027 AFDMSO Area Forecast Discussion National Weather Service Missoula MT Issued by National Weather Service Great Falls MT 327 AM MST Fri Jan 10 2025 .DISCUSSION... KEY MESSAGES: - Widespread moderate mountain snow starting Friday afternoon. - Valley snow Saturday and Sunday. Waves of moisture can be seen both on satellite and radar moving into the Northern Rockies currently. Westerly winds gusting 20 to 30 mph at ridgetop will primarily down slope valleys and provide upslope flow to our north south mountain ranges today. Saturday as the bulk of moisture departs to the southeast, flow aloft becomes northwesterly and widespread light snow is possible both Saturday and Sunday. Impacts and Timing: Snow-covered roads are expected at the passes and elevations above 4000 feet in north-central Idaho by the afternoon commute. Interstate 90, from Lookout Pass to Saint Regis, may see reduced visibility due to moderate snow rates, along with gusty westerly winds between 25-30 mph, between 4 and 5 pm. Snow accumulations in the mountains are still expected to range between 6 to 12 inches by Sunday afternoon, with 3 to 6 inches expected at the passes along the ID/ MT border and Marias Pass. The foothills and valleys of the Swan Range have about a 25% probability of receiving around 6 inches of snow. The valleys along and east of Highway 93 in western Montana, as well as Grangeville in north-central ID, have a 40 to 50% probability of receiving up to 2 inches of snow. Another weak ridging pattern will set up over the Northern Rockies by mid-week next week, with increasing probabilities for the return of fog and stratus. Long Range Forecast: An increasing number of ensemble members (30 to 40%) are hinting at a potential cold outbreak, with Arctic air sliding south out of Canada around the 18th. Stay tuned for further details and updates on the likelihood of occurrence. && .AVIATION... Valley fog is sloshing around both Missoula and Flathead Valleys again today. KGPI has the better chance to experience IFR or worse conditions (3 miles or less visibility) through 10/1400z. The next weather system is already producing 30 to 40 kts west winds at 700mb and valley inversions should break mid to late morning, improving any visibility or ceiling issues at area terminals. Precipitation will spread across the region during the afternoon causing terrain obscurations. Light snow is expected to cause both ceiling and visibility issues for periods of time on Saturday. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$