Persistently warm temps mean avalanches are likely
The recent run of warm weather has created significant avalanche danger in the Salt Lake City-area Wasatch Mountains, says Drew Hardesty, forecaster at the Utah Avalanche Center.
"As we transition from a winter to a spring snowpack, we get into the dire old melt-freeze cycle," he told The Park Record Tuesday. "Once that cycle is thrown out of whack, as it is currently and has been for the last four days, then we start to see unstable, wet avalanche conditions."
The main issue is not that temperatures are high during the day, but that, for the past several days in a row, they’re not dipping below freezing at all. Normally, melting snows during the day will freeze back up at night.
"At night that free water will lock up as it naturally goes to that freeze phase. And that’s great — that’s what you want. That develops large, rounded corn snow grains," he said. "And then you start to develop what I would call good plumbing within the snowpack through what we would call percolation columns. So you can see water that percolates down to the bottom of the snowpack and then just comes out. And you can see it running down the roads or streets or what have you.
"But the cause for concern is that we’ve gone three and in some cases four and even more nights without a good re-freeze and so we just continue to have melt and melt and melt and melt. And a little bit of water within the snowpack is OK, too much is not."
Canyons Snow Safety personnel reported a skier-triggered avalanche in an out-of-bounds area southwest of the Ninety-Nine 90 peak near Dutch Draw called Cone Head, around 1 p.m. Monday. The two-feet deep "wet slab" avalanche was around 40 feet wide and ran 400 feet down the mountain, according to the report.
The "lone skier" who triggered the avalanche lost one ski but was able to ski off the slab. He is lucky to be alive, Hardesty said.
"Super lucky. I mean, like in the dry-snow avalanches, it’s just powder snow and often it can be a little bit more of a catch-and-release situation. But this stuff is like churning concrete and so I’m just shocked that he was able to get off.
"It’s worth noting that that’s the exact same spot as a fatality back in January of 2005," he said.
Latest Utah Avalanche Center Forecast (as of Tuesday, March 17)
SLC-area Wasatch Mountains:
"Areas of CONSIDERABLE danger exist in the mid and upper elevation northwest to east facing terrain for wet loose and wet slab avalanches. Human triggered wet slabs 1-3′ deep remain possible. Remember it’s more difficult to get untangled from flowing wet avalanches and they set up like concrete in the deposition zone. Elsewhere the danger is MODERATE.
"The avalanche danger will rise to MODERATE and human triggered slides are possible on all steep snow covered slopes, especially during the heat of the day. Avalanches triggered in steep, rocky terrain have the potential to break deeper and wider than you might expect and could get quickly out of hand.
Most other terrain offers a LOW avalanche danger."
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