Instability on Silver Peak

New snow amounts of around 12 inches existed in this area by mid afternoon. Snowfall rates were near or in excess of 1 inch per hour for much of the morning. Wind loaded areas held wind slabs up to 2 feet thick in the most heavily wind loaded areas. Widespread instability was observed in the areas traveled between 7,000' and 8,000' on N-NE-E aspects both above and below treeline at the old/new snow interface. At this interface a 1 inch thick (2cm) layer of early stage facets formed from melt-layer recrystalization existed above the rain crust from the March 3 rain event. This facet layer was an unstable weak layer with the new snow above it acting as the slab. Slopes steeper than 37 degrees were required to put slab avalanches into motion due to a fairly high coefficient of friction of the slab against the bed surface. Slopes in the 30 to 36 degree slope angle range cracked when skier weighted, but did not avalanche. Shooting cracks up to 50ft in length were observed. The early stage facets at the old/new snow interface were a consistent failure layer throughout the day.

Photos 1 & 2: Small crown from skier triggered test slope failure.

Video 1: More info on photos 1 & 2 plus a second ski cut.

Photo 3: 50 foot shooting crack on N aspect just east of the snowpit location (noted lat/long) in wind loaded near treeline terrain.

Video 2: Wind transport of storm snow along the east ridge of Silver Peak.