HELENA, Mont. (AP) — The National Weather Service has issued a winter storm warning for the Great Falls, Helena, Butte and Bozeman areas from Thursday morning through mid-day Friday.

Officials are forecasting up to 18 inches (46 centimeters) of snow on mountain passes in central and southwestern Montana with up to a foot (30 centimeters) of snow in the Bozeman and West Yellowstone areas.

Travel could be difficult as blowing snow decreases visibility in some areas. The roads could get icy if snow melts and re-freezes and night, the weather service said.

The Gallatin National Forest Avalanche Center issued a backcountry avalanche warning Thursday for the Bridger, Gallatin and Madison mountain ranges and the Lionhead area near West Yellowstone. Over a foot of heavy snow and strong winds are overloading a weak snowpack, creating dangerous avalanche conditions.

“If there is visibility, which there isn’t, you would see natural avalanches breaking on wind-loaded slopes,” center officials said in their report. “And if you get on a steep slope you’ll likely trigger and get buried in an avalanche.”

The weather service has issued winter weather advisories in the Missoula and Billings areas.

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