Avalanche risk is high in much of the western U.S.
BOISE, Idaho — As a massive winter storm dumped snow across much of the western U.S., some hardy winter sport enthusiasts headed to ski resorts and backcountry slopes despite frigid temperatures during the long Martin Luther King Jr. Day weekend.
But in many areas, the storm brought a high risk of avalanche conditions along with the wind and snow, with fatal results.
In northern Idaho, two men were rescued after they were caught in an avalanche Thursday afternoon, while the body of a third man in their backcountry skiing group was located Friday. On Thursday night the occupants of two vehicles escaped without injury after an avalanche buried their cars in another part of the state.
The first reported U.S. avalanche death of the season happened Wednesday in California, on a section of expert trails at the Palisades Tahoe ski resort near Lake Tahoe. Four people were trapped and one was killed in that slide. A second avalanche struck the same area the following day, with no reported casualties.
Here’s a look at why, when and how avalanches occur, and some tips on how to stay safe from slides: forecaster with the U.S. Forest Service Panhandle Avalanche Center. “It’s kind of like a cake: You might have a nice thick layer that’s good and cohesive, and then a thinner layer of frosting. Then put another cake on top of that, and throw in the factor of a slope angle or steep terrain.”
Extra pressure on top of that snowpack “cake,” from wind, rain, heavy snow or motion can cause some of the layers to shear off and slide down the slope, Bernall said.
Sometimes that slide happens in the form of loose snow, called a “sluff.” Sluffs account for only a small percentage of deaths and property damage from avalanches, according to the Sierra Avalanche Center.
But many avalanches are made up of slabs, where a large layer of snow breaks away and slides down the mountainside. Those account for most fatalities.
Another kind of avalanche occurs when wind creates a cornice of snow that hangs over a ridge or the edge of a steep slope. An overhanging mass of snow can fall suddenly, catching anyone standing underneath or on top of the cornice by surprise, according to the Colorado Avalanche Information Center.
What triggers them?
Movement, rapidly changing weather, wind — any one of these things can cause an avalanche. But experts say 90% of the avalanches that cause injuries or deaths are triggered by the victim or someone with them.
That means that people who ski, snowmobile, snowshoe or enjoy other activities in the snowy backcountry should check the avalanche forecast before they head out, and make sure they have the right safety gear.