SAC Preliminary Report
Two skiers hiked/traversed into CLOSED uncontrolled terrain at Mt. Rose. This terrain had NOT BEEN OPENED, HAD NOT BEEN SKIED, and HAD NOT BEEN CONTROLLED this winter. It is more analogous to a backcountry snowpack. They decided to drop into a steep wind-loaded slope. The first skier triggered a large avalanche that swept him 600-1000 ft downslope and buried him n debris that averaged 5 ft deep and reached up to 10 ft. deep in some areas. The second skier immediately called 911 and the search for his partner continued for the rest of the day.
The avalanche that this skier triggered likely started as a wind slab failure and stepped down onto the persistent weak layer of facets near the base of the snowpack. The slab was a mix of 1F (1-finger) and 4F (4-finger) hardness snow sitting on top of F (fist) hard facets. This avalanche started on a 40-45 degree slope and pulled out adjacent slopes that reached up to 50 degrees in steepness. The slopes that released were mostly N aspects with some NE aspects on the skier's left of the paths. The initial avalanche was likely 350-550 ft in width and connected multiple start zones. It was at least a D3 on the destructive size scale. The crown measured between 3 and 5 ft. in depth.
Later in the day after continued wind loading and snow accumulation, explosive control work triggered additional similar avalanches that started as wind slabs and stepped down to the old persistent weak layer. Ski cuts on small wind loaded test slopes caused shooting cracks and wind slab failures up to 16 inches deep.
Searchers located the buried skier around mid-day 12/11. Avalanche dog teams from Mt. Rose, Sugarbowl, Squaw Valley, Alpine Meadows, and Placer County narrowed the search area down to a large pile of debris where two of the avalanche paths came together. Washoe County Search and Rescue Team Members then probed this area and located the buried skier. He was buried under 220-260 cm of avalanche debris. This debris was from the slide he triggered as well as subsequent avalanches released during control work to create a safe area for searchers to operate in.