12-13

Skiers on found a very poor snowpack structure on Mt. Wheeler. A slab of new snow rest on very weak facets, a good recipe for an avalanche. Photo: A. Whitmore

In some areas that had a thin snowpack in January, a persistent layer of facets exist near the ground. In this case they are buried just over 2.5 feet deep. In other areas they can be found in the middle of the snowpack but buried at about the same depth.  Photo: J. Welz

This small steep slope on Mt Ellis in the northern Gallatin Range is a sign of unstable conditions. It was skier triggered and broke about 20 feet wide but didn't run downhill more than a few feet due to low slope angles. Photo: J. Wareham

This avalanche was triggered after two skiers descended the Hellmouth Couloir (upper right of photo). They were traversing approximately along the line of the arrow and triggered the avalanche near the red X where the snowpack was only 2 feet deep. Photo: B. Vandenbos

This avalanche broke 1-5 feet deep but it averaged 2.5 feet deep.  It occurred on a NNE aspect at 9030 feet. It was triggered at the red X in a shallow area as skiers traversed onto this slope. Photo: B. Vandenbos

A thin weak layer of small facets was easily seen in the avalanche crown.  In other locaations, a similar layer was very obvious in snowpit walls and propagated fractures in stability tests. In isolated locations this layer produced collapses which are a clear sign of instability. Photo: GNFAC