Up to 40 inches of snow is possible in some mountain ranges of northwestern Montana.

Blizzard conditions will be possible for a time due to howling winds that could gust up to 40 mph.

The snow may be heavy enough to shut down travel.

The calendar may say September, but the weather will feel wintry in the northern Rockies this weekend.

Heavy snow – up to 3 feet in some areas – and temperatures in the 20s and 30s will bring an early taste of winter to portions of Montana, Idaho and Wyoming from Friday through Sunday.

In the mountains and intermediate elevations, a general 1-2 feet of snow is forecast to fall, AccuWeather said, and up to 40 inches is possible in some mountain ranges of northwestern Montana.

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Blizzard conditions will be possible, the National Weather Service in Great Falls, Montana, warned, because of howling winds that could gust up to 40 mph.

"This early-season winter storm and/or blizzard has the potential to set a new benchmark for snow accumulations, cold temperatures and resulting impacts for parts of the Northern Rockies and the Rocky Mountain Front," the weather service said.

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"Extreme impacts are possible, including to the power infrastructure (widespread power outages), agricultural and ranching interests, recreation (camping and hunting activities) and travel. Widespread significant tree damage is possible with the expected heavy, wet snow and strong winds," the weather service said.

AccuWeather said that enough snow is likely to fall to cause substantial travel delays through the mountains and over the passes. The snow may be heavy enough to shut down travel.

"There will be heavy accumulation on the roads over the passes with this storm," AccuWeather meteorologist Brett Anderson said.

The cause of the cold will be the jet stream, which will take a sharp, southward plunge from western Canada into the Northwest late this week, the Weather Channel said. That will send temperatures crashing well below average for this time of year.

Instead of winter, folks in the southeastern USA will see temperatures more typical of midsummer for at least the next several days. Some record highs are possible.