Observation: Public

Observation Details

Signs of Unstable Snow

Observations

We tied ourselves to a tree and lowered down onto a consequential 35 degree north, northeast slope at 6200' Temp was 25F, no wind, snowing lightly. The Christmas crust sandwich is very stout and took effort to saw through. However, it is topped by a couple inches of snow, which has a light rain crust from last night, and then another couple inches of snow on top of that. This skied nicely above 6300 where there is deeper snow over last night's crust, but below that elvation, it was dust on crust and not that pleasant (down or up). In fact this layer failed on isolation in a compression test and slid easily off the block. We did two compression tests and had sudden planar failures on 12 and 16, 60cm down on the 11/18 crust (which has deteriorated). This was our first sudden planar result in the Mission Ridge area and it was startling. Previous failures had al been either resistant planar, or even non-planar. Because of this new behavior, we did a propagation saw test which failed at 30/100 and not only slid uniteruppted to the end of the column, but also pulled about half of the loose granuals below with it, exposing the ground. The column tipped over as it slid due to crushing the layer of concern (which used to be a hard crust and now is loose crystals). I have a video, but can't figure out how to upload it here. Our conclusion was that this lower layer might be hard to trigger through the stout Christmas crust sandwich, but if that layer is triggered and a slab pops out, it will be very high consequence. We opted not to ski any avalanche terrain in the area.