Wind Slab Avalanche on Andesite Ridge

Location Name: 
Andesite Ridge
Region: 
Donner Summit Area
Date and time of avalanche (best estimate if unknown): 
Fri, 02/19/2016 - 13:51
Location Map: 
United States
39° 21' 2.7684" N, 120° 21' 56.0772" 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: 
42degrees
Trigger type: 
Other - explain below
Crown Height: 
1 ft
Aspect: 
Northeast
Weak Layer: 
Storm Snow
Avalanche Width: 
60ft.
Terrain: 
Above Treeline
Elevation: 
8 120ft.
Bed Surface: 
Storm Snow
Avalanche Length: 
250ft.
Number of similar avalanches: 
1
More detailed information about the avalanche: 

An oven sized cornice piece dropped onto an E-NE facing wind loaded slope triggered this wind slab avalanche. The wind slab failed on a density change within the storm snow at the base of the wind slab and the crown measured between 12 an 18 inches in depth. The starting zone for this slide measured between 38 and 42 degrees in steepness. Active wind loading was taking place on this slope at the time it failed. Other nearby wind loaded slopes looked like they had already slid during the storm early yesterday morning. 

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

Some light snow started in this area around 1:45 pm.