This avalanche ran during the Feb 20 storm event that put down 14" of new snow capping off a week long storm event that totaled 18" at 1.2" SWE. Strong SW winds early in the cycle built pencil hard slabs 2'-3' thick on N and E aspects at treeline and above. These were resting on the previous week's 5" that preserved the Feb 11 faceted layer. Stability tests and an intentionally triggered slide early in the week indicate that failure first occurs on the Feb 11 weak layer before stepping down into facets beneath the Christmas Rain Crust and or going to the ground. In the case of this avalanche, a combination appears evident with numerous step downs visible on the bed surface.
This avalanche was first noted in an observation by Sam Van Wetter on Feb 20.
Sam Van Wetter photo.
Forecaster photos.
