Large D3-R5 avalanche on Silver Peak

Location Name: 
Silver Peak
Region: 
Cabin Creek, Deep Creek, or Pole Creek Area
Date and time of avalanche (best estimate if unknown): 
Sun, 12/19/2010 - 10:30
Location Map: 
United States
39° 13' 14.4624" N, 120° 14' 45.3084" W
See map: Google Maps
US


Red Flags: 
Recent avalanche activity
Whumphing noises, shooting cracks, or collapsing
Recent loading by new snow, wind, or rain
Obvious avalanche path
Observation made by: Forecaster
Avalanche Observations
Avalanche Type: 
dry,slab,
Slope: 
36degrees
Trigger type: 
Natural
Crown Height: 
3 ft
Aspect: 
East
Weak Layer: 
Other
Avalanche Width: 
600ft.
Terrain: 
Above Treeline
Elevation: 
8 350ft.
Bed Surface: 
Other - explain below
Avalanche Length: 
1 000ft.
More detailed information about the avalanche: 

This natural avalanche likely occurred within 2 hours prior to arrival as debris were very fresh. Evidence of powder cloud 15' above snow surface on trees at the end of debris field. We were unable to access the crown on flanks due to unstable conditions and exposure from adjacent avalanche paths.

The exact failure layer is unknown but flank depth suggests that the failure occurred at or above the height of the Dec 17 surface hoar layer. With minimal propagation of sympathetic D2 avalanches along the flanks, buried surface hoar was probably not the failure layer. A density change within the storm snow was most likely the weak layer in the avalanche.

Avalanche Photos: 
Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
100% of the sky covered by clouds
Air temperature: 
Above Freezing
Wind Speed: 
Strong
Precipitation: 
Rain
Air temperature trend: 
Warming
Wind Direction: 
Southwest
Accumulation rate: 
Less than 1 in. per hour
More detailed information about the weather: