Vail & Summit County

Avalanche

Jason Konigsberg, Ron Simenhois · Apr 25, 2019 · Vail & Summit County

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Weather

Warm and mostly sunny with a light, cool breeze at above treeline elevations.

Snowpack

Snowpack was supportable to skis with just a couple inches ski penetration as we moved off the trail. The surface snow was moist on all aspects to about 12,000 feet but no signs of instability were observed. Northerly-facing slopes held dry, cold snow above that. Wetting below the top 3 to 4 inches of snow on northerly above and near treeline slopes was minimal. Lots of very small rollerballs from the past few days, out of rocky terrain but none gaining any mass. This was just the recent new snow losing cohesion as it saw the sun for the first time and nothing more than that.---We went over to a southwest-facing, thin snowpack (HS = 60 cm), rocky, steep area and found very different conditions. The snowpack was unsupportable and we would sink to the ground while bootpacking. Collapsing of well-defined depth hoar beneath a wet snowpack. This was the site of a Wet Slab avalanche reported on Wednesday.

Avalanche

We went and checked out a large Wet Slab avalanche that was previously reported on Wednesday, April 25. As reported the avalanche released on a southwest-facing slope, above treeline at 12,400 feet. The avalanche was triggered remotely as the skier descended supportable, refrozen surface snow. The avalanche released about 50 feet below the skier. The crown of the avalanche was about 150 feet wide and 2 feet deep. Although this was confirmed to be a Wet Slab avalanche, the avalanche released in a similar fashion to some of our March avalanches, entraining the entire snowpack and knocking over trees in the run out. The size of the avalanche was quite impressive for one with a crown of only 2 feet.---Although the skier was skiing on a supportable snow surface when he triggered the avalanche, the entire snowpack was wet and saturated down to large depth hoar at the ground. As we bootpacked through soggy snow down to the avalanche we initiated more collapses. We talked about how we too could have been easily fooled by the supportable snow surface and how it is important to step out of your skis or off of your snowmobile to truly feel if the snowpack is wet beneath superficial melt-freeze crusts.