Vail & Summit County
AvalancheAndrew McWilliams · Dec 14, 2022 · Vail & Summit County
Weather
Started and ended cold and windy. Single-digit temperatures with 20-30 mph winds and stronger gusts from the northwest. Light snowfall all morning without significant accumulation. Winds were swirling around the Coon Hill basin.
Snowpack
New snow was blown into stiff slabs and drifts near and above treeline. These slabs ranged in hardness from 4-finger to pencil and in places there was less than 5cm of ski penetration. The thickness of these new slabs varied from 5cm to 30cm but were on average about 15cm thick. Due to the stronger winds, these slabs extended into the near treeline elevation band and produced numerous collapses and shooting cracks as I ascended. I remotely triggered a small avalanche on a wind-loaded slope near treeline. The crown was 10-15cm deep and it ran on facets. This small slope actually faced northwest (into the ridgetop wind direction), but because the winds were swirling in the basin, they were loading this slope. This small slope was likely very thinly covered prior to this storm and the new slab was resting on facets that extended to the ground. Extended Column Tests still showed propagating results in the older snow in pits on southeast and northwest aspects suggesting that the persistent slab problem is still active in this area. A smaller wind slab avalanche might step down into older snow and become a larger persistent slab avalanche. Coverage on west aspects near and above treeline at the tunnel was spotty. Isolated areas have deeper pockets of snow, but many places are bare ground or exposed willows. NW to SE aspects had more consistent coverage.
Avalanche
I remotely triggered a small avalanche near the Eisenhower Tunnel (Coon Hill) on a northwest aspect near treeline on a small test slope.