Northern San Juan

Avalanche

Josh Jespersen · Dec 28, 2022 · Northern San Juan

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Observation photo 1Observation photo 2

Weather

During a brief lull in the storm today ambient temperatures rose from around 10AM to 1PM with OVC sky and L winds before the air temp got considerably colder ahead of the next pulse of snow which started around 130PM.

Snowpack

BTL storm snow gained some cohesion during the temperature rise and cracking/collapsing was observed. As we ascended towards ATL there was less cohesion and less signs of instability. Poor structure did persist under the canopy with the new snow on top of our fully faceted base. Along the ridge, there was a wind crust embedded between the new and old snow and almost no cohesion in the storm snow which was bonding well to that crust. Upon descending signs of instability grew as we got nearer to the BTL storm snow that had formed a slab and was producing shooting cracks and small avalanches on top of the PWL. However, the snowpack got significantly shallower as we descended and the sub-structure reduced in depth to a small layer only about 10cms deep near the end of our run.

Avalanche

Descending the gully we were staying high skiers left and trying to avoid being pulled into the bottom of the gully. This was manageable, but with the gutless base conditions of purely faceted snow it was not easy to maintain speed and stay as high as we wanted to near the end. Exiting the gully there is a small opening with steeper walls on either side that can be managed with maintaining speed and moving quickly from one point to the next. I was barely able to quickly clear the area, but my partners skis sunk into the facets in the center of this feature. As that happened, she tried to shuffle out but unbeknownst to her due to the small size of the avalanche, the fact that it propagated behind her, and the structure of a very soft slab over a non-planar PWL the avalanche piled around her legs up to her waist before she could get out of the way. The avalanche released simultaneously from both the ESE and NNW aspects on either side of the gully. We had to shovel out her feet and unbury her skis.