Big winds gusting to 70 miles an hour ahead of snowstorms in western Colorado have brought “high danger” avalanche warnings, expected to stay in place through Saturday as snow builds up in the high country.
The Colorado Avalanche Information Center and National Weather Service have issued warnings of dangerous conditions around the mountainous west side of the state, similar to warnings in California, Idaho and Montana following heavy snowfall.
Avalanches last month temporarily closed Loveland Pass and skiers triggered slides in Summit County.
CAIC officials have recorded more than two dozen significant avalanches this year and typically document around 5,000 a year crashing down from mountains in western Colorado, drawing from reports filed by a widening network of participants who file reports. Director Ethan Greene estimated as many as 50,000 avalanches occur each winter.
The problem is avalanches that hit people and vehicles. Avalanches kill an average of six people a year in Colorado, state records show. Deaths numbered 7 last winter and 12 in 2021.
High danger warnings covered mountains near Crested Butte, Steamboat Springs and Glenwood Springs. The exceptionally strong winds that began Thursday night can either increase or reduce avalanches depending on the terrain and direction, Greene said. In some areas, wind blasts away snow that has built up along ridges, reducing the potential for slides.
“But, in general, wind is really bad for avalanches. It increases the load in avalanche start zones,” he said. “You can end up with ten feet of snow in a start zone from drifting. And wind can create harder, super-dense layers that, when avalanches are triggered, create very destructive debris flows.”
Avalanches occur in the high mountains as the result of snow accumulating on steep slopes, typically between 30 degrees and 45 degrees. If the snowpack becomes unstable, sudden weight can trigger a release of tension and snow rapidly falls with force great enough to destroy trees and buildings. Most of the fatalities have resulted when backcountry snowmobilers, skiers, and hikers put weight on unstable slopes.
Traditionally, backcountry mountaineers protected themselves by analyzing wind, snow buildup, and slope stability before moving through terrain prone to avalanches. CAIC since 1983 has provided increasingly detailed forecasts.
“Back in the day, it was more on individuals to assess things,” Greene said. “Now you can start with these forecasts. We can arm you with huge amounts of information.”