Western US faces high risk for avalanches Christmas week

By Brett Rathbun, AccuWeather.com Meteorologist

December 23,2015; 8:35PM,EST

 

 

The threat for avalanches will be high in the western United States over Christmas weekend, as a large number of winter sports enthusiasts prepare to get out out their skis and snowmobiles.
A persistent train of storms since November across the West has consistently caused new layers of snow to fall, some loose and some compact.
Avalanches are triggered when there is a compact layer of snow above a loose layer of snow. The compact layer acts like a sheet of smooth ice that can quickly become detached from the loose layer below.
When this occurs, an avalanche can barrel down a mountain slope posing a life-threatening risk to outdoorsmen in its path.

Locations within a high risk for avalanches include the southern Bitterroot Mountains of central Idaho, northern Wasatch Mountains of northern Utah, Gallitan and Madison ridges of southwestern Montana and portions of the Colorado Rockies.
According to the National Avalanche Center, these areas have very dangerous avalanche conditions and travel in this terrain is not recommended.

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According to the Northwest Avalanche Center (NWAC), a party of snowmobilers were caught in a slide over the weekend in Cooke City, Montana. One person was killed, marking the second avalanche fatality of the season in North America.
"Dangerous conditions will persist here in the Northwest with the consistent storms we are having," the NWAC warned on Facebook.
"Please make good decisions and ride cautiously. Carrying the gear and knowing how to use it is a good step."
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Back-country skiing can become extremely dangerous and is not permitted in areas of a moderate to high risk of avalanches.
"Skiers that choose to ignore signs and ski on unstable runs are taking their lives into their own hands," AccuWeather Meteorologist Becky Elliott said.
The main conditions that can start an avalanche include the slope of the terrain, the conditions of the current snowpack and various triggers including new snow, skiers and wind, according to the National Avalanche Center (NAC).
Avalanches generally occur across mountain areas that slope greater than 35 degrees.