A combination of high winds, heavy snowfall in the mountains and rising temperatures prompted the Flathead Avalanche Center to elevate the avalanche danger to “high” Thursday morning.

The advisory applies to the Flathead, Swan and Whitefish mountain ranges and the southern portion of Glacier National Park.

While it was raining in the Flathead Valley on Thursday morning, there was heavy snow in the mountains, said Erich Peitzsch, interim director of the Flathead Avalanche Center.

And there has been a rapid warming trend up to mid-elevation slopes.

“The snowpack doesn’t like rapid change,” he said.

In addition, strong winds have been causing snow loading on slopes. A weather station at 7,000 feet in the Middle Fork recorded wind gusts exceeding 100 mph Thursday and a station at Logan Pass in Glacier National Park recorded gusts up to 118 mph at 9 a.m.

“The issue is consistent winds” that transport snow from one side of a ridge to another, increasing new snow slab depths, Peitzsch said.

“Wind is the architect of avalanches,” Peitzsch said. “And it’s loading on top of layers of weak, lighter snow. Heavy on top of light is not a good scenario.”

BNSF Railway avalanche safety personnel reported several natural avalanches on both sides of the canyon west of Marias Pass in the Middle Fork corridor Wednesday.

Peitzsch said he was in the Middle Fork on Thursday morning, observing signs of snowpack instability.

“Visibility was poor so we couldn’t see surrounding areas for avalanche activity,” he said.

Advisories typically remain in effect for 24 hours, and they are issued on Wednesdays, Saturdays and Sundays. But given the changing circumstances, Peitzsch said there could be frequent updates over the next few days.

Avalanche advisories can be found online at: http://www.flatheadavalanche.org.

Reporter Jim Mann may be reached at 758-4407 or by email at jmann@dailyinterlake.com.