avalanche site in Wyoming
© Chris Leigh
An area near Jackson Hole, Wyoming, where snowboarder Jed Wesley Foster, triggered an avalanche on 19 January 2015.

11 have died this month, in Washington, Colorado, Wyoming and elsewhere, due to 'poor snow structure' and increased interest in backcountry skiing

This year has been a deadly one for avalanches. Ten people have died in the past 10 days, and a total of 14 have died this snow season in the US, according to the Colorado Avalanche Information Center. With 11 deaths this month, it's the highest death rate for January since 2008 and the second worst January in 20 years.

There were four deaths just last weekend alone, with one person killed in Washington state, two skiers killed in Wyoming and one snowmobiler killed in the Whitefish Mountains.

But the spike in fatalities has not occurred because of an increased number of avalanches, according to avalanche forecaster Spencer Logan of the Colorado Avalanche Information Center. The center's data shows that the number of avalanches recorded this season "are not out of the ordinary". Rather, Doug Chabot, director of the Gallatin National Forest Avalanche Center believes the high death rate is due to a "perfect storm" of conditions.

Some areas in the west have "poor snow structure", meaning they have weak snow layers, or snowpacks, which can easily lead to avalanches when they can't support the weight of heavier snow on top of them. These can be caused by long periods of no snowfall, according to Logan who said the Rocky Mountains recently saw "a period of relatively dry weather". And while Chabot says weak layers of snow are fairly common, the snowpacks have been "especially weak" this year.

"It would kind of be like building a big house on top of a crumbling foundation. It's not going to work," Chabot said.

On top of that, large numbers of people have been going into the backcountry to ski, snowboard and snowmobile. Backcountry skiing is "a growing recreation segment", according to Chabot. As more people traipse through non-regulated ski areas that have not been groomed for avalanche control with explosives, it's more likely that someone will hit a weak spot in the snow.

"The weight of one person hitting a weak spot, a spot that's especially weak, can create a big avalanche," Chabot said. "It's hard to believe but an 150 pound person can trigger the side of a mountain and an avalanche. Until you've seen it, you think it's impossible but it's not."

avalanche awareness field trip
© Elaine Thompson/AP
Students and instructors head up a hill on snowshoes during an avalanche awareness field trip for teenagers, at Mount Baker, Washington on 11 January 2016.
Those killed by avalanches over the past few weeks have been "a mixed group activity-wise", according to Mike Rheam, avalanche forecaster for the Bridger-Teton National Forest Avalanche Center. They've ranged from skiers and snowboarders to hikers and snowmobilers. The incidents have also been widespread, with fatalities in Colorado, Utah, Wyoming, Montana, Washington and Alaska.

Avalanches can be caused by a number of factors, but Chabot believes "the theme is the same this year" across the West, with weak snow layers giving out. While the Rockies commonly see weak layers of snow because of cold and dry weather, the Pacific Northwest can see large snowfall followed by rain, which can either flush out lower layers or become crusty and weak itself.

There's also been a more widespread risk of avalanches across the West, according to Rheam.

"Usually there's specific areas where the avalanche hazard might be heightened and other areas where it can be low," he said. "This year everyone's getting snow and everyone seems to have some avalanche hazard."

Despite these dangers and the high number of fatalities, people are free to travel the backcountry as they please. Logan believes "one of the great joys is that you are responsible for yourself and you get to make the decisions". However forecasters continue to warn the public about the dangers of potential avalanches, especially since many of the deaths have involved "flawed decision making", according to Rheam.

"If you're going to go into the backcountry, you need gear and you need education," Chabot said. "It's imperative and so we really encourage people to get both."