Vail & Summit County
AvalancheBill H · Jan 16, 2014 · Vail & Summit County
Weather
Clear, Sun, 30 deg, calm to light wind..
Snowpack
The snowpack was ~0.5 m deep on S and W aspects that were baked off or wind-stripped prior to recent storm cycle, and 1m+ on sheltered W and NW aspects in the trees. It was often much deeper in wind loaded features. New wind slabs, 0.1-1m+ thick ranging from 4F+ to 1F, were built by cross loading on the S/SE aspects of the west facing ribs that extend from Chicago Ridge back towards Tennessee Pass. Wind slabs were touchy, with extensive cracking and propagation on convex features, but reluctant to move on the low angled terrain. We experienced multiple collapses in the flatter sheltered meadows (10-30m radius from group) near treeline, which were triggered by skiers entering the open terrain. The storm snow load on top of old snow and basal facets was repeatedly collapsed by the additional weight of 1-2 skiers. We observed a natural avalanche (within last 24 hrs) on a steeper S aspect. Additionally, a skier triggered windslab on SW facing terrain propagated fully around to the W aspect of rib.
Avalanche
1) S aspect, 11800 ft, SS-NC-R2/D1.5-I Natural release from cornice drop onto wind slab. 2) W aspect, 11,800 ft, HS-ASc-R2/D1-I or O Triggered on ski cut, slab released, broke into couch-sized blocks and moved downhill >10m. Slope angle was lower, ~30deg. Cracks propagated from slab, wrapping around terrain feature to W/NW aspect across over 50m of low-angled terrain.