If being in the midst of winter last week and then suddenly getting hurled into spring has you feeling a bit unsteady, you aren’t alone.
The Utah Avalanche Center on Tuesday extended its high danger warning, which was put in effect on Sunday morning, until Thursday as warming continues. Forecaster Dave Kelly said the quick flip between cold and warm conditions has brought a lot of uncertainty to the state’s snowpack, which doesn’t like change.
There were between 3 and 5 inches of new snow across the Wasatch Range last week while temperatures in Park City early this week reached the low 60s. The daytime heating has created areas of unstable wet snow that carry a high likelihood of slides.
Kelly said this avalanche cycle is different from what forecasters saw last week, particularly in Little Cottonwood Canyon, when slides caused by new, heavy snow were more common.
Most mountain locations have been hovering around freezing for several days, which means there hasn’t been a strong refreeze of snow overnight. Sunshine throughout the day causes the snow surface to deteriorate quickly, Kelly said, which leads water to seep deeper into the layers of the snowpack.
The combination of the dry snow from last week and the warming creates the potential for dangerous wet slab avalanches that can flow far and fast like a river, according to Kelly. The unprecedented amount of snow may also cause the slides to travel farther than is typical.
“We’re dealing with two different beasts. Last week, we were dealing with the winter snowpack and now we’re dealing with a snowpack that is transitioning,” he said. “There’s always a reasonable amount of uncertainty when you go through your first warm-up at any point, but it’s the combination of all the snow from last week, all the snow from all season long and how warm the temperatures are.”
A skier on Friday reported a wet snow slide that occurred on Iron Mountain. The individual reported the 6-inch deep, 70-foot wide slide traveled into a gully, about 500 meters down. An avalanche around 100 feet wide near Scott’s Bowl likely triggered by a cornice overnight was observed the following day.
Cornices that have formed with the mountain ridgelines have also become a concern as their sensitivity increases amid rising temperatures. Cornice falls can trigger an avalanche on the slope below, and the Utah Avalanche Center said these kinds of slides are certain while danger is high.
Glide avalanches are also a common threat this time of year as cracks open with continued warming. Kelly said these slides could also trigger wet slab avalanches as they travel down the slope.
Colder temperatures, specifically those at night, are crucial to helping the snowpack heal and reducing the risk of avalanches. Kelly said conditions usually become more predictable as the snowpack settles into the spring cycle.
“It’s a pattern that makes sense. There’s more uncertainty during this transitional time,” he said.
Until then, Kelly advises backcountry users to avoid slopes steeper than 30 degrees. People should also be aware of their proximity to avalanche terrain and should stay away from slopes off of or under avalanche runouts.
More snow is expected later this week, though it isn’t likely to elevate avalanche danger.
The daily avalanche forecast and additional information can be found on the Utah Avalanche Center website, utahavalanchecenter.org.