Special advisory issued: Avalanche danger is high

The Flathead Avalanche Center issued a backcountry avalanche warning for the entire advisory area on Friday, Feb. 13.

That includes the Whitefish Range, Swan Range, Flathead Range and portions of Glacier National Park. The center said new snow, above-freezing temperatures and strong winds had created highly unstable conditions.

The center warned that both natural and human-triggered avalanches are likely, and they rated the avalanche danger as “high” on all slopes in their advisory area.

“Very dangerous avalanche conditions exist,” the center said. “Travel in avalanche terrain is not recommended, and avalanche runout zones should be avoided.”

From two to nine inches of new snow has fallen in the center’s advisory area over the past 24 hours. The SNOTEL site at Flattop Mountain in Glacier Park reported 0.9 inches of snow-water equivalent, while the Noisy Basin site near Jewel Basin on the Swan Range reported 0.1 inches.

Temperatures increased to above freezing in many locations on Feb. 12. Snow levels climbed to nearly 5,500 feet, and winds on ridgetops were extreme at times.

A weather station in the Middle Fork area recorded 100 mph wind gusts on Feb. 13, and a weather station at Logan Pass in Glacier Park recorded 118 mph wind gusts the same day. Winds move snow around the mountains and helps to create the potential for slab avalanches, especially when the new snow piles up on weak layers.

Avalanche safety personnel for BNSF Railway reported several naturally occurring avalanches on both sides of the John F. Stevens Canyon on Feb. 12 — large enough to bury and injure a human. The slides occurred on north, southeast and east aspects. Slab crowns ranged from 20-30 centimeters, and crown width ranged from 15-20 meters.

The Montana Department of Transportation warned drivers about avalanche dangers on U.S. 2 from West Glacier to Marias Pass. Vehicles are not allowed to stop alongside the highway. For a detailed message, call 406-257-8402.

Avalanche control personnel at Whitefish Mountain Resort were kept busy bombing hazardous areas, but they reported mixed results. They characterized the snow conditions affected by higher temperatures as “upside down” snow pack.

For more information, visit online at www.flatheadavalanche.org.