Damaging wind and feet of mountain snow will blast Northwest Montana beginning late Wednesday as Old Man Winter gives it one last hurrah.

Describing the next few days as a "long-duration, high-intensity atmospheric river," the National Weather Service in Missoula is warning residents across the state to be prepared for blizzard conditions, downed trees, power outages and even rockslides.

Strong winds pick up Thursday morning, with gusts up to 50 mph in valley locations. Mountains could see localized gusts up to 80 mph.

Due to the subtropic origins of the weather system, snow levels will rise to about 4,000 feet on Wednesday. Above that line, 3 to 6 feet of snow is possible in all mountain ranges of Northwest Montana.

A winter storm warning for the West Glacier, Polebridge and Essex region lasts through Saturday. Expect up to 7 inches low lying areas, with 20 to 40 inches on Marias Pass south of Glacier National Park.

"This will be a very wet system," the Weather Service cautioned in its Tuesday forecast.

"Travel or recreation in the backcountry during this timeframe will be dangerous to impossible, expect blizzard conditions at times, downed trees, and feet of heavy, wet snow."

Areas prone to rockslides include Lolo and Lookout passes, Montana 200 east of Missoula and on U.S. 93 near Lost Trail Pass south of Hamilton.

In the Flathead Valley, overnight lows Saturday will dip into the teens.