Utah Avalanche Center warns midweek warming could lead to wet avalanches
Backcountry users encouraged to avoid terrain traps
March 7, 2017
After a large cornice fracture triggered a massive out-of-bounds avalanche along the Park City ridgeline last week, Craig Cordon, a forecaster with the Utah Avalanche Center, is encouraging backcountry users to avoid similar terrain.
On Thursday, what appeared to be a natural cornice broke off at around 10,000 feet causing a 400-foot slide carrying 10 to 15 feet of debris that snapped several large trees, according to the Utah Avalanche Center. The website states that heavy snowfall and persistent winds have led to "very large" cornices along upper elevation ridge lines, especially along the Park City ridgeline, a prominent area for cornice development.
"Cornices are unusually large, and as we do start to warm up they will easily break well behind you," Gordon said. "They can be triggered naturally at any given time of the day so the best advice, since they are so unpredictable, is to simply avoid being on or underneath any of these."
Most of the resorts and backcountry areas of the Wasatch and Uinta Mountains received more than 12 inches of new snow over the weekend, Gordon said. He added, "What really changed the avalanche conditions overnight were the strong winds that accompanied the new snow." He said the winds created drifts that are sensitive to the additional weight.
"Spring is the fight between winter and summer. You get these storms that roar in and they are often accompanied by strong winds, which means that new snow is going to be sensitive," Gordon said. "Once the sun comes out and is high in the sky, you have to change gears from a winter snowpack perspective to thinking that cold snow will get damp and the steep, sunny slopes will start to get reactive."
A warming trend over the next couple of days will likely produce temperatures in the upper 40s by the end of the week, Gordon said, adding "depending on how rapidly that takes place it will set the tone for what the hazard is."
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Gordon advised skiers, snowboarders and snowmobilers traveling outside of the resort's boundaries to be aware of the elevations they are riding on because upper elevation snow can quickly turn into something "a little more damp and wet."
"Keep an eye on new snowfall this time of year and an eye on temperatures, especially if those start to rapidly warm. Snow doesn't like rapid change it gets cranky in a hurry," Gordon said. "If it goes through a rapid change, especially this time of year, wet avalanches will become the main focus for the backcountry."
However, Gordon said the current snowpack is deep, strong and relatively stable. He said mostly new snow avalanches are generally occurring right now, which is "good news because those are predictable and it's pretty straight forward."
"When we have got a shallow snowpack or weak layers, things become a lot sketchier and a lot less predictable," Gordon said. "The possibility for avalanches to break deep and wide under those circumstances adds to those complexities."
As the temperatures gradually warm up over the next few days, Gordon suggested avoiding what he referred to as "terrain traps," such as gullies, creek beds and road cuts. He said even a small avalanche could pile up a significant amount of deep, dense snow.
"With those types of characteristics, you don't have to a huge avalanche because a wet slide is just like a slab of concrete," Gordon said. "It's a funny time of year because with the new snow you can certainly work the different aspects and elevations, but, really, the biggest thing this time of year is as the snow gets damp you want to get off and out from under deep sun exposed slopes."
For more information about current avalanche conditions, go to https://utahavalanchecenter.org.
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