Avalanches on Andesite Ridge - Natural and Skier triggered

Location Name: 
Andesite Ridge
Region: 
Donner Summit Area
Date and time of avalanche (best estimate if unknown): 
Wed, 12/29/2010 - 12:00
Location Map: 
United States
39° 20' 57.5952" N, 120° 21' 57.5856" 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: 
Skier
Crown Height: 
2 ft
Aspect: 
East
Weak Layer: 
Storm Snow
Avalanche Width: 
60ft.
Terrain: 
Near Treeline
Elevation: 
8 100ft.
Bed Surface: 
Storm Snow
Avalanche Length: 
250ft.
Number of similar avalanches: 
3
More detailed information about the avalanche: 

Photo 1: Skier triggered slide at 7700 ft on an ENE facing, wind-loaded, 38 degree slope on Andesite Ridge.

Photo 2: Skier triggered shooting cracks in the same area

Photo 3: Natural avalanche that occurred during the night (between midnight and 3 am most likely) on an ENE facing wind-loaded, 40 degree slope at 7500 ft.

Video: Slide triggered with a ski cut on a wind-loaded E aspect at 8100 ft. Map location and avalanche information corresponds to this slide.

All of these avalanche broke on a storm snow weakness within the new snow just above the old/new snow interface.

Avalanche Photos: 
Avalanche observation video: 

Avalanche triggered by a ski cut on Andesite Ridge.MOV

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: 
Greater than 1 in. per hour
More detailed information about the weather: