Gunnison
AvalancheZach Guy · Feb 9, 2015 · Gunnison
Weather
Calm to light winds, warm, few clouds.
Snowpack
South aspects: Multiple layers of wet crusts and facets to the ground on N/BTL slopes. As we approached ridgetop, there was ~3″ of wet recent snow that was easily sluffing on steep pitches. North aspects above treeline: The slopes we observed were mostly wind scoured with large sastrugi features. A few crossloaded pockets. No signs of instability on steep slopes. North – East aspects near treeline: Snow profiles on Peeler Peak and on Schuykill Ridge showed the Jan 11 surface hoar layer 35 – 40 cm deep, propagating in extended column tests (ECTP M, sudden collapse, Q1). Deeper weak layers were indistinct and unreactive in tests. See profiles North-Northeast aspects below treeline: As we descended in elevation, the slab over SH lost cohesion due to faceting and was shallower in depth (<15 cm thick), and the surface hoar became spotty in distribution in semi-gladed terrain. The snowpack felt entirely faceted with the exception of a few isolated pockets of wind-stiffened snow. Full trapdoor skiing at lowest elevations. No signs of instability on steep slopes.
Avalanche
We skier triggered two persistent slab avalanches failing on the Jan 11 surface hoar layer, one of which sympathetically triggered another slide, on N to NE aspects near treeline on Peeler Peak. The slides were 1 to 1.5 feet deep. One failed 500 feet wide and sympathetically pulled out another slab about 200 feet away. They were on small features and ran roughly 150 vertical feet. SS-AS-R3-D1.5-O, SS-ASy-R1-D1-O, and SS-AS-R2-D1-O. Interesting notes: 1.) They were both triggered by the second skier from low on the slope, after the first skier had jumped around on the slopes attempting to trigger them. 2.) A large portion of the largest slide ran on slope angles below 35 degrees, with the slab pulling out on a slope as low as 20 degrees.