Fog and a layer of low clouds will slow warming across western Montana this morning, and that’s shifting today’s forecast from valley rain to valley snow.

By mid-afternoon, the atmosphere becomes unstable, and models show bands of heavier snow showers developing, especially near I-90 around 3 PM. These bands could produce up to an inch of snow per hour, causing a sudden drop in visibility and rapidly changing road conditions. Because of this, the Winter Weather Advisory for the Missoula and Bitterroot Valleys is being extended, and short-term Snow Squall Warnings may be issued during the afternoon commute.

Winds will generally stay around 20 mph but could gust to 40 mph in stronger showers. After sunset, westerly winds strengthen, valley downsloping increases, and snow is expected to transition back to rain, while mountain areas above 4,500 to 5,000 feet continue to see 1 to 2 feet of snow and blowing snow through Saturday.

Another disturbance brings continued precipitation into Sunday, followed by yet another system on Tuesday. Snow levels briefly drop below 4,000 feet late Saturday, rise Sunday, and could fall again Tuesday night as colder air returns.

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WINTER STORM WARNING is in effect from now until 4 PM Saturday for Highway 11 Pierce to Headquarters, Highway 12 Lowell to Lolo Pass, Pierce, Dixie, Elk River, and Elk City for 2 to 6 inches of snow in the valleys and 9 to 18 inches in the higher terrain.

WINTER STORM WARNING is in effect from now until 5 PM Saturday for Lolo Pass and Highway 93 Sula to Lost Trail Pass for 1 to 5 inches of valley snow and 8 to 15 inches of mountain snow, with wind gusts up to 40 mph on Friday.

WINTER STORM WARNING is in effect from now until 5 PM Saturday for Highway 83 Seeley Lake to Condon, I-90 East Missoula to Bearmouth, and Highway 200 Bonner to Greenough for 5 to 10 inches of snow.

WINTER STORM WARNING is in effect from now until 5 PM Saturday for I-90 Lookout Pass to Haugan, Highway 200 Trout Creek to Heron, Evaro Hill, and Highway 200 Thompson Falls to Plains for 1 to 4 inches of valley snow and 8 to 14 inches of mountain snow.

WINTER STORM WARNING is in effect from now until 2 PM Saturday for Absaroka/Beartooth Mountains and Crazy Mountains for 12 to 24 inches of snow, with mountain-top wind gusts up to 50 mph.

WINTER WEATHER ADVISORY is in effect from now until 11 PM this evening for Missoula and Bitterroot Valleys, north of Hamilton in the Bitterroot Valley and Missoula for moderate to heavy snow showers with snow rates of 0.5 to 1 inch per hour and wind gusts up to 40 mph.

WINTER WEATHER ADVISORY is in effect from now until 11 PM this evening for Butte and Blackfoot Region including Butte, Georgetown Lake, Homestake Pass, Highway 12 Garrison to Elliston, and MacDonald Pass for 1 to 6 inches of snow with wind gusts as high as 35 mph.

WINTER WEATHER ADVISORY is in effect from now until 11 AM this morning for Elkhorn and Boulder Mountains, including Montana City, Homestake Pass, Elk Park Pass, Clancy, Wickes, Corbin, and Boulder for up to 1 inch of snow.

WINTER WEATHER ADVISORY is in effect from now until 11 AM this morning for Gallatin Valley, including Bozeman and Gallatin Gateway for up to 1 inch of snow.