Vail & Summit County
AvalancheKreston Rohrig · Jan 10, 2019 · Vail & Summit County
Weather
Calm day with little wind. Clouds increased to fully overcast by mid-afternoon creating flat light conditions for the descent.
Snowpack
I was hoping to dig near the crown of a very-large avalanche that occurred sometime between Sunday and Monday, but there was too much hangfire left in the path to be safe. Instead I dug on a north facing aspect near to the path and found a weakened snowpack capped by a stout wind-slab. The recently formed slab was only 20cm thick just off the leeward side of the ridge. Below this, dense slabs were faceting but still supportable through the upper and mid-pack. The bottom 60cm of the snowpack was weaker than I've seen in other places and consisted of larger grained facets and some small 3mm depth hoar near the ground. It's not surprising that the snowpack is weaker here in the eastern part of the zone where seasonal snow totals have been less and the snowpack is thinner. Attached pit profile shows a classic upside down snowpack.
Avalanche
The avalanches previously reported from this area pulled out mid-path near treeline. The slopes generally face west, but the wind-loaded side of the chutes wrap almost to north. Given what I saw in another pit nearby, I believe that the cross-loaded sides of the paths loaded with SW winds and overwhelmed the weak snow layers near the ground. What was still visible of the crowns showed they failed deeply into the snowpack and likely went to ground.