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Health, Science & Environment

‘Tis the season for avalanches: why increased snowfall can cause riskier conditions

backcountry skier in snow
Annie Putman
/
KUER
When avalanche conditions are risky, backcountry skiers take to lower-grade slopes where a slide is less likely.

More than two dozen avalanches were reported over the weekend to the Utah Avalanche Center and 11 of them were caused by skiers, snowboarders and snowmobiles.

Mark Staples, director of forest service for Utah Avalanche Center, said early season snows formed weak layers that became the foundation of the snowpack.

“It's just like building a house. If it's got a weak foundation and you keep adding floors onto the house, that foundation won’t be able to support it anymore,” Staples said.

He said it’s normal to have this many avalanches but what’s notable is that many of them are being triggered from miles away. Staples said it’s important to know how easy it is to trigger a snow slide.

“A major red flag is you can cause an avalanche just as you're walking near a slope,” he said. “You can be underneath it, on top of it, inside of it, and your weight collapses that weak layer because that weak layer extends that slope out to where you are. It collapses and then a fracture can shoot out anywhere from 60 to 100 miles an hour.”

Jim Steenburgh, professor of atmospheric science at the University of Utah, calls it a tale of two kinds of snowpacks. He said some areas are more prone to avalanches, like north-facing sides of mountains.

“Those areas are where the early season snow didn’t melt out, and so that snow there [is] basically rotted, it became very weak,” he said. “The other side of the compass, the south side, all the snow melted off and so it never developed these weak layers.”

But incoming storms predicted to hit Utah later this week could create more dangerous conditions on top of the weak snowpack by adding weight to the snow.

When we start getting more snow later this week, that's going to create avalanche problems everywhere because the new snow could cause avalanche hazard to go up even in the areas that are low right now,” Steenburgh said. “But those kinds of avalanche problems tend to settle out fairly quickly. The situation we have is in the north side, people call that a ‘persistent weak layer.’ It takes a long time for it to heal up.”

Last year Utah had the deadliest ski season in years where four people died in an avalanche. Staples suggests checking avalanche forecasts before heading out and to stay safe and vigilant. He said it’s best to avoid terrain that’s steeper than 30 degrees.

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