Observation: Public

Observation Details

Triggered Avalanches

Signs of Unstable Snow

Observations

Key notes with regard to the weather and snowpack form sunday was the warming in temperature, the two reactive interfaces in the snowpack, and the reactive wind drifted snow. Aside from these attributes the snowpack was strong and supportive.

The most recent storm deposited 20-30cm of new low density snow at 6000f and continued on sunday to snow 1cm/hr at timest. Buried surface hoar that formed late last week, was observed 25cm down, on the interface prior to the weekend storm and contributed to the release and run of dry loose snow avalanches. This also could be contributing to the sensitivity of the skiier-triggered wind slab we intentionally released on test slopes at ridge crest. The low density storm snow was gaining cohesion throughout the day BTL as the freezing level gained el. . THe upper storm snow also was cohesive enough to propagate a fracture NTL and ATL from the drifting snows from Sundays wind.

Pit tests revealed reactive sudden results on the Jan 29th interface with buried SH and January 24th crust down 55cm with associated rounded-facet grains. Compression tests did provoke sudden high quality failures but did not result in propagation in large column tests. (See media for East Slopes North, Josh Hirshberg has several good images showing this structure).

We began to observe wind drifting snow loading features 6000ft and above. Cracking and collapsing were also indicators of the upper pack instability as we travel on a cross loaded ridge above 6000ft.