A staggering 287 people have died in Colorado due to avalanches over the past 70 years. To put that number into perspective, that’s nearly twice the number of fatalities that have occurred in the state with the second highest avalanche-related death toll – Alaska (158). States like Washington (130), Utah (120), Montana (119), and California (66) have similar alpine topography, but land nowhere near Colorado’s number of fatalities. This begs the question – why are Colorado’s Rocky Mountains seemingly that much more dangerous?
The snow is different here
The same dry and sunny high-elevation climate that makes Colorado so desirable for skiing also results in some of the highest avalanche risk in the country.
“The reason why Colorado has a lot of fatalities is that we have a pretty thin snowpack,” says Mike Cooperstein, avalanche forecaster at the Colorado Avalanche Information Center (CAIC). “We call it a continental snowpack. It’s dry, thin, and cold here. It’s not like California, Oregon, [and] Washington, where the snowpack is usually pretty warm and deep.”
In the fall, the fate of Colorado’s seasonal avalanche risk is already brewing.
“We get early season snow in October, November, and it sits around on high-elevation, north and east-facing slopes where it’s pretty cold,” says Cooperstein. “And the snow goes through changes when it sits on the ground like that.”
Most years, that deepest layer of snowpack becomes weak over time, according to Cooperstein. It turns into what’s been dubbed “sugar snow”– the kind of snow that can’t be packed into a snowball. The layer is called depth hoar and it can last for a long time, concealed underneath waves of snowfall.
“If those weak layers fail, we get what we call dry slab avalanches,” says Cooperstein. “And those are pretty dangerous avalanches. They can be big, they can break up above people, they can break wider than you might think, and they can break deeply in the snowpack.”
A typical black diamond trail at a ski resort has a slope angle of around 25-45 degrees. That’s the kind of pitch where avalanche risk starts to get scary, especially in Colorado where that deep, weak layer is known to give way. Slides can be triggered spontaneously, by the stresses of weather or by the sheer weight of the snow. Of course, a slide can also be triggered by the weight of a person or a group of people, pushing the strength of the snow beyond its breaking point.
So many people
Human traffic can increase avalanche risk. That’s where Colorado’s massive ski culture comes in, quite visible in the Saturday morning I-70 exodus of eager Denverites to the mountains. Granted, many of these travelers are headed to resorts, but some are headed to the backcountry. Having such high traffic on dangerous slopes around the state is also likely to contribute to a higher number of avalanche fatalities.
“There’s pretty easy access to the mountains here,” says Cooperstein. “You can drive to the top of the passes, whereas in a lot of other places in the western United States, they just close those roads for the winter and you can’t get access.”
A changing climate?
Climate change is reportedly making safety more complicated for people entering the backcountry. It’s causing more variability between seasons, says Jeff Derry, executive director of the Center for Snow and Avalanche Studies.
Derry says, “We’re seeing ‘extremer’ extremes in our weather.”
Consider the past few years.
The 2017 snowpack was heavy and wet–“a different kind of snowpack than what we’re used to seeing. It kind of resembled the maritime snowpack,” says Derry.
Then 2018 “hit a near record low.” According to Derry, a thinner snowpack can actually make avalanche risk greater in some cases.
“We saw a major major avalanche cycle,” says Derry. Reported avalanches that season totaled at 4,273, compared to the 2,500 annual average statewide. Cumulatively, 92 avalanches reportedly caught a total of 135 individuals in their path. Eight people lost their lives.
The future of avalanche risk
Looking forward, it’s been reported that a higher level of unpredictability can be expected. But what does that mean for avalanche danger? Unfortunately, there’s no simple answer.
“It might throw you out of your wheelhouse,” says Derry. “In the sense that you might be used to a certain snowpack and all of a sudden you’re seeing these conditions that aren’t normal in your region, wherever they may be.”
Since the nature of avalanche conditions can vary so much by region, backcountry travelers might be privy to the typical risks on their local mountains, but naive to those elsewhere.
Before heading out into the backcountry, it’s recommended that one take a class from the American Institute for Avalanche Research and Education (AIARE) to learn best practices specific to a location.
“You gotta know your area, you gotta know where you’re going,” says Derry. “Get the training, be prepared, go to the CAIC website, have all the right gear, and stay informed on recent and current conditions.”