770 FXUS65 KMSO 131919 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 119 PM MDT Sun Apr 13 2025 .DISCUSSION... KEY MESSAGES: - Decreasing clouds with warming temperatures as high pressure builds through Tuesday. - Weather becomes unsettled by Wednesday with snow accumulating along the Continental Divide, including mountain passes above 5000 feet, through Thursday. High pressure will move into the Northern Rockies today and help clear out cloud cover and any lingering valley fog, providing a sunny Monday and Tuesday for the region. High temperatures will rise into the 70s Tuesday afternoon for valleys of central Idaho, and into the upper 60s to 70s for valleys of western Montana. Overnight low temperatures during this time will still be quite cold; ranging in the 30 degree range for most valleys. With high temperatures warming into the 70s on Tuesday, a very noticeable drop in temperatures will occur by Thursday. Temps will drop nearly 20 to 30 degrees by Thursday, resulting in high temperatures along the Continental Divide only reaching the upper 30s to low 40s Thursday afternoon. This change will be the result of a vigorous and deep low pressure system driving south of the region and allowing for much colder air to infiltrate the Northern Rockies. Along with this low pressure system, precipitation in the form of snow will occur down to about 5000 feet, with the emphasis of snowfall focused along the Divide. Moderate confidence exists that mountain passes such as Marias, MacDonald, and Homestake will feel the brunt of the snowfall, with middle-of-the- road (50th percentile) estimates ranging from 3 to 6 inches Wednesday night through Thursday evening. Cities such as Butte, Georgetown Lake, and Anaconda could see up to 2 inches of snow Thursday morning before melting. There is less confidence in amounts below 4000 feet, given differences between forecast models on how far west the low pressure system will shift. If it moves further west with time, additional locations across western Montana into central Idaho may have more to speak of regarding snowfall and higher amounts of precipitation. In addition to area wide precipitation, gusty northeast to easterly winds will be present late Wednesday through Thursday across all of western Montana and north central Idaho. There is the potential for enhanced wind gusts greater than 40 mph in valleys that are north-south oriented; ie: the Bitterroot valley, the corridor from Deer Lodge to Butte, highway 93 from Lost Trail Pass to Leadore. Both precipitation and gusty winds will dissipate on Friday as high pressure returns. && .AVIATION...VFR conditions are expected through Tuesday as high pressure ridging slowly builds in. Winds will be light and diurnally driven, becoming breezy by Tuesday afternoon. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$