‘Deadly avalanches are likely’ in the coming days, experts warn (updated)
Predicted snow, wind threatens to overload already weak snowpack
Avalanche experts Tuesday forecasted the highest possible level of danger as heavy snowfall and strong winds loaded snow atop what they say is already an exceptionally weak snowpack, adding that natural and human-caused avalanches are “certain.”
“Deadly avalanches are likely in the Utah backcountry over the next few days,” the Utah Avalanche Center said in a statement Monday. “… Routes you have used successfully for years may not be so safe now, and everyone should reassess travel routes and take extraordinary precautions.”
The first week of February was one of the deadliest on record, according to the avalanche center, with 15 backcountry fatalities across the United States. In January, two fatal avalanches struck just outside the gates of the Park City Mountain Resort.
And earlier this month, four people were killed in an avalanche in Millcreek Canyon.
Recent avalanche fatalities in Utah and Colorado have occurred on terrain that backcountry users consider safer, less steep routes. An unusual snow pattern has caused extraordinary backcountry conditions, making even traditionally safe routes potential killers.
On Tuesday, the center forecasted “extreme” avalanche danger for both the Uinta region and Salt Lake region, the latter including the Park City ridgeline.
The center classifies extreme avalanche danger as when natural and human-caused avalanches are certain to occur, and in this year’s snowpack, they warn those avalanches will run farther, wider and deeper than normal.
Scores of recent reported avalanches populate the center’s website, some of which ran for more than 1,000 vertical feet. And on Tuesday, the center reported a large-scale natural avalanche cycle in Little Cottonwood Canyon during which multiple avalanches ran over the road.
In addition to traveling with a partner and avalanche safety equipment — including a beacon, shovel and probe — experts stress the importance of staying away from steep slopes and traveling only on slopes that have less than 30 degrees of pitch.
They caution that even mellow slopes can be dangerous if they are below an area that has steeper portions, with multiple recent observations reporting remotely triggered slides from safer nearby terrain.
With a persistent weak layer of snow sitting almost at ground level, the slides that have broken down to that layer have taken with them the entire season’s snowpack, running wider and farther than normal. That can affect traditional notions of which routes are safe or protected from avalanche dangers.
The center issued an avalanche warning through Wednesday morning for high country in much of Utah, including the Wasatch Range and Uinta Mountains. The danger was expected to persist for days.
Monday’s forecasted danger was “high” for both the Uinta region and the Salt Lake region, and then increased to “extreme” as winter weather battered the region. Each level on the center’s scale represents twice the danger of the previous level, meaning if “moderate” indicates a danger level of four, extreme indicates a danger level of 32.
Tuesday’s forecast indicated three factors adding to the danger, including buried weak layers of snow, wind-drifted snow and newly accumulated snow. Winds can load snow onto a slope 10 times faster than the snow falls, according to the avalanche center, which reported sustained westerly winds averaging 15 to 30 mph, with gusts of 60 to 80 mph at higher elevations.
The forecast says that snowfall greater than 1 inch per hour can overload the snowpack and lead to many natural avalanches. The center predicted multiple periods of snowfall greater than 1 inch per hour through Wednesday.
The Cottonwood canyons, the Park City ridgeline and the Uinta Mountains each received a foot or more of snow, with several feet predicted for some spots.
Mark Staples, director of the Utah Avalanche Center, said in an observational video posted Friday that the persistent weak layer near the ground, which dates back to the earliest storms of the season, can be found almost everywhere.
“We’ll see if this layer can ever heal by the end of the season,” he said.
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Utah’s legislative general session is set to end on Friday, and if history is any indicator, there will be a flurry of floor amendments and last-minute changes for county officials to monitor.