Jan Wesner Childs
Thirty-six people have died in avalanches in the U.S. since Dec. 18, according to the Colorado Avalanche Information Center. That ties the highest number ever recorded in any season dating back to 1950.
Only two other seasons since 1950 have seen as many avalanche deaths – 2007-08 and 2009-10.
This year’s deadly conditions started with early-season snowfall, followed by a dry spell. That created in the snowpack what experts call a persistent weak layer, buried under subsequent layers of snow as winter kicked into full gear.
"And then it’s like a house of cards," Jim Donovan, emergency management director in San Juan County, Colorado, told weather.com.
A skier, a snowmobiler, a hiker – any movement – can cause the weak layer to fail and send layers of snow careening down a slope, carrying and burying anything and anyone in its path.
Donovan, who also heads up the Silverton Avalanche School, is one of several avalanche experts who spoke to weather.com about this year's historic season and the weather that brought it about.
(WATCH: Utah Avalanche Caught on Camera)
Temperature gradients in the snowpack caused that early layer of snow to go through a process called faceting, which weakens snow and turns it to a granular consistency that doesn’t stick together, explained Mike Cooperstein, an avalanche forecaster at the CAIC.
Commonly called “sugar snow,” it's more the consistency of salt.
"By itself, it’s not a big deal. But then when you put more snow on top of it, when you put an additional load on top of it, that weak, sugary snow down near the ground can’t support the load of snow on top," said Greg Gagne, a forecaster at the Utah Avalanche Center. "It’d be like trying to build a house on top of a foundation made of sand. It’s just a very unstable structure."
Such conditions aren't unusual on a local level.
"We see this maybe every 10 years," Donovan said. "But what was unique [this season] was that it was so widespread."
The persistent weak layer was in play across much of the western U.S., contributing to avalanches in states including Colorado, Wyoming, Montana, Utah and Idaho.
One of two deadly avalanches in Donovan’s county left three victims buried under as much as 20 feet of snow. Volunteer search and rescue teams worked for days to dig them out.
The victims are among 12 killed in Colorado, which also ties a record.
(MORE: Latest Winter Weather Forecast)
Simon Trautman, an avalanche specialist at the National Avalanche Center, said another unique thing about this season is that the threat never really subsided.
"You have direct action avalanches as the danger is rolling through but then you also have this period of latent danger that can continue for quite some time," Trautman said. "So what happened this year was the danger didn’t really drop between storms, it just stayed high."
The center maps avalanche risk on its website at Avalanche.org. Orange means there is considerable danger. Red means high.
"During February, that whole map was elevated," Trautman said. "It was either orange or red for the entire time."
The first death of the season came when a 41-year-old snowmobiler named Brandon Jones triggered an avalanche in the Salt River Range near Afton in western Wyoming, one week before Christmas.
It happened on a slope known to locals as "Suicide Mountain."
A report by the Bridger-Teton Avalanche Center, one of 14 backcountry avalanche information and education centers run by the U.S. Forest Service, singled out a persistent weak layer formed after snow that fell in mid-November was followed by about three weeks of dry conditions before more snow accumulated.
The most recent death was March 27 near Matanuska Glacier northeast of Anchorage, Alaska. Erin Lee, 40, was skiing the backcountry when she was killed.
The deadliest incident was Feb. 6 in the Mill Creek Canyon area outside of Salt Lake City when seven backcountry skiers from two different groups were caught up in a slide. Survivors worked frantically to dig out those buried in the snow, according to a report from the CAIC. Four people died. Two others were pulled out alive.
(MORE: Avalanche Deaths On The Rise)
The conditions we saw this year could be a window into future winters under the influence of climate change, according to Dr. Jordy Hendrikx, director of the snow and avalanche lab at Montana State University.
Hendrikx said it would take extensive research to specifically link the conditions to climate change, but they are in line with what is expected as temperatures increase and weather patterns shift.
"And what I mean by that is that we are seeing longer periods of low to no precipitation, so longer periods of drought, followed by more extreme periods of precipitation thereafter. It’s consistent with the types of behaviors that we expect to see in a future climate," Hendrikx said.
"It’s really been the perfect storm of meteorological conditions to lay this foundation."
Hendrikx finds avalanches to be unique among weather-related disasters because they are most often triggered by human decisions. They're different than earthquakes in California, for example, where there is almost a constant risk and little residents can do to avoid the threat.
"Whereas in the case of avalanches we see that in 90% of cases where there’s a fatality either the person that was killed or a member of the person’s group triggered that avalanche," Hendrikx said. "So what that means is that we as humans and our decisions we make and how we use terrain and how we choose to expose ourselves has a direct connection to the ultimate outcome and the consequence."
As is usual, most of the 36 people killed in avalanches this season were in backcountry areas, which are often located on public lands like national forests or similar wilderness areas. Avalanches are rare in ski resorts because the private entities that own them carry out extensive monitoring and mitigation actions, including triggering avalanches to clear the risk.
Skiers, especially, are attracted to the backcountry despite the risk.
"You’re just flowing down the mountainside in snow that is knee-deep, waist-deep," Gagne said. "All the noise in your life, everything just shuts off, and you’re just focusing on just using gravity flowing downhill. It’s a euphoric feeling."
At the beginning of the season, there were concerns that more people would be killed in the backcountry this year due to an influx of inexperienced people seeking more open spaces in the wake of the coronavirus pandemic. That hasn't been the case – many, if not most, of those killed were well-versed in the dangers of trekking into the snow-covered wild.
Often they were equipped with the recommended gear – a beacon, probe, shovel and, in some cases, an avalanche air bag – and had training in how to spot and navigate through avalanche terrain.
But as Gagne points out, there’s a saying: "Everyone knew you were an expert, except the avalanche."
"I like that because it’s basically saying you cannot outsmart it," he said. "At the end of the day, the snow’s going to have its way."
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.
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