Avalanche warnings have been issued across several regions of Montana amid forecasts of continuing snow in the state, including in one area where two snowmobilers in Minnesota died last week that has seen over a foot of additional snow since.
The forecasts for Friday into the weekend include more heavy snow, high winds and the possibility of rain.
"Slabs of new and drifted snow will be thick and easily triggered by the weight of a person or snowmachine," a warning from The Flathead Avalanche Center said. "In isolated areas, avalanches may break in weak layers of old snow near the ground. Travel in avalanche terrain is not recommended."
The warnings have been enacted across areas of western and northern Montana, including Cooke City, north of Yellowstone National Park.
Cooke City is where two snowmobilers died in a separate avalanche last week, and an estimated 15 inches of snow has fallen since then.
"If you get onto any steep slope, even one that isn't wind-loaded, expect to trigger a slide beneath the new snow," the warning from the Gallatin National Forest Avalanche Center states. "If you need added incentive to stay out of avalanche terrain, remember that there are weak layers lower in the snowpack that could break even deeper."
Snow slid onto Interstate 90 west of St. Regis, including in at least one spot where it covered the westbound lanes, the Montana Department of Transportation said.
A 33-mile (53 kilometer) stretch of westbound lanes, from St. Regis to the border of Idaho atop Lookout Pass, will be closed overnight. The agency will reevaluate the conditions on Saturday morning.
Jon Swartz, the maintenance administrator for the DOT, told NBC Montana he did not know if the slides hit or trapped any vehicles. Some disabled semi tractor-trailers were also blocking the interstate, the DOT said.
Eastbound traffic was moving over Lookout Pass, but with delays, the Montana Highway Patrol said.
In northwestern Montana, the avalanche danger was listed as high in the Whitefish Range, in the Flathead Range including a portion of Glacier National Park and in the Swan Range, the Flathead Avalanche Center said.
In west-central Montana, the avalanche danger was high near Lolo Pass, in the southern Mission mountains along with the Rattlesnake and southern and central Bitterroot mountains, the center said. All elevations will be impacted by heavy snow and increased hazards.
"The likelihood of avalanches will increase with continued wind, snowfall, rising temperatures and rain at lower elevations," the West Central Montana Avalanche Center said.
Strong winds created new snowdrifts that were 2 to 4 feet (61 to 122 centimeters) deep and wind-loaded slopes were expected to experience avalanches, the Gallatin center said.
The City of Missoula and its Office of Emergency Management said Thursday officials were "exercising caution" in issuing an urban avalanche warning for Mount Jumbo, closing the mountain to recreation. The closure also applies to private property.
In February 2014, an avalanche that started on Mount Jumbo destroyed a house, burying two residents. One of them died later died of her injuries, while her husband was hospitalized for weeks.
The 2014 slide also buried an 8-year-old boy and partially buried his older sister as they played in the backyard of another residence at the base of Mount Jumbo. The girl was able to dig herself out. The boy, who was found an hour later, survived because he ended up in an air pocket.
The Montana Department of Transportation on Friday reported strong winds and severe driving conditions in the Browning area—east of Glacier National Park—and black ice was reported on roads in extreme northwestern Montana, near the Idaho border.
The Associated Press contributed to this report.
