Small natural and human triggered wet loose snow avalanches on Andesite Ridge.

Location Name: 
Andesite Ridge
Region: 
Donner Summit Area
Date and time of avalanche (best estimate if unknown): 
Thu, 12/29/2011 - 10:30
Location Map: 
United States
39° 21' 0.828" N, 120° 21' 43.956" W
See map: Google Maps
US


Red Flags: 
Recent loading by new snow, wind, or rain
Rapid warming
Obvious avalanche path
Observation made by: Forecaster
Avalanche Observations
Avalanche Type: 
wet,loose,
Slope: 
37degrees
Trigger type: 
Natural
Aspect: 
Northeast
Weak Layer: 
Old Snow
Avalanche Width: 
8ft.
Terrain: 
Near Treeline
Elevation: 
7 760ft.
Bed Surface: 
Old Snow
Avalanche Length: 
120ft.
Number of similar avalanches: 
3
More detailed information about the avalanche: 

One natural avalanche and 3 human triggered wet loose avalanches in this area. Wet snow on all N-NE-E aspects traveled up to high point of 7,850'.

Photo 1: Small natural wet loose avalanche with location and other details listed above. Avalanche likely occurred during the early morning hours on Dec 29.

Photo 2: Small skier triggered wet loose avalanche on creekbed wall, 7,720' E aspect 42 degree slope angle. Location is just above and to climbers left of avalanche in photo 3.

Photo 3: Another small skier triggered wet loose avalanche on NE aspect 38 degree slope angle. Location 39.35100, -120.36356.

Video made in lower angle terrain just south of the avalanches at 39.3435, -120.36150.

Avalanche Photos: 
Avalanche observation video: 

20111229 Andesite Ridge 001.MOV

Weather Observations
Blowing Snow: 
No
Cloud Cover: 
100% of the sky covered by clouds
Air temperature: 
Above Freezing
Wind Speed: 
Light
Precipitation: 
None
Air temperature trend: 
Warming
Wind Direction: 
Southwest
Accumulation rate: 
More detailed information about the weather: