Observation: Public

Observation Details

Observed Avalanches

Signs of Unstable Snow

Observations

We broke into the near alpine to assess how the wind and cold temps had worked on the recent storm snow. Weather was -10c, BKN, NO precip, light to moderate winds from W at ridgeline, turning SE by late afternoon, light transport west to east mid-day before winds shifted. HS was 180-200cm at 6400' on a 25 degree NE slope near adjacent 40-50 degree slopes. These adjacent slopes likely ran and pulled some of the snowpack mid-storm on Sunday 26 December and have since reloaded.

We found two facet layers of concern, one 40cm down on a 2cm wind crust and another 70-80cm down and corresponding to the high pressure. Both facet layers were 1-1.5mm and well-developed. Our test results showed a CTM12 on the 40cm facets and CTM14 on the 80cm facets, both with sudden planar results (Q1). ECTN 24 @40cm down. Cornice drops yielded inconsequential dry loose sluffing or no avalanches (AC-0), but the paths we dropped them to had likely already run in previous storms.

Our take-away: at this leeward location winds have transported recent storm snow into 1F slabs over F or 4F- facets that overlay a recent wind crust and the solstice crust. In adjacent, sheltered locations these shallow wind slabs are topped by low density cold smoke and are not noticeably reactive under foot during travel.

At 5500' on a 30-degree SE aspect we also noted a sandwich of two sun crusts with small radiation recrystallization facets between them, but did not perform any tests. This is another layer to watch moving into the next storm cycle.