Cornice Triggered Wind Slab Avalanche on Andesite Ridge

Location Name: 
Andesite Ridge
Region: 
Donner Summit Area
Date and time of avalanche (best estimate if unknown): 
Sat, 03/12/2016 - 13:30
Location Map: 
United States
39° 21' 2.4228" N, 120° 21' 56.3904" 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: 
40degrees
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: 
2
More detailed information about the avalanche: 

This wind slab avalanche was triggered by intentionally dropping oven and dishwasher sized pieces of cornice onto the wind loaded slope below. The first dishwasher sized piece of cornice triggered the debris in the skiers left of the photo and occurred about an hour previous to the second part of the slide. The second piece of cornice dropped onto the slope about an hour later at 13:30 triggered the skiers right side of the slide. The crown was estimated between 12 and 16 inches. The slope angle on this ENE facing slope measured between 42 and 38 degrees on the convex start zone.  

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: