Wind Slabs on Andesite Ridge

Location Name: 
Andesite Ridge
Region: 
Donner Summit Area
Date and time of avalanche (best estimate if unknown): 
Sat, 01/23/2016 - 13:30
Location Map: 
United States
39° 21' 2.016" N, 120° 21' 55.1916" 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: 
39degrees
Trigger type: 
Other - explain below
Crown Height: 
1 ft
Aspect: 
Northeast
Weak Layer: 
Storm Snow
Avalanche Width: 
100ft.
Terrain: 
Above Treeline
Elevation: 
8 100ft.
Bed Surface: 
Storm Snow
Avalanche Length: 
300ft.
Number of similar avalanches: 
2
Number of people caught: 
0
Number of partial burials: 
0
Number of full burials: 
0
More detailed information about the avalanche: 

Wind slab avalanches 12 to 18 inches in depth occurred when oven sized pieces of cornices were intentionally dropped onto wind loaded slopes. The wind slabs failed at the interface between the last nights snow and Friday's snow surface. Slope angles in the start zones varied from 35 to 45 degrees and aspects ranged from NE-ENE. 

Photo 1: Smaller avalanche on a smaller slope triggered by an intentional cornice drop. Slope is at 8000 ft. in above treeline terrain.

Photo 2: Larger wind slab avalanche also triggered by an intentional cornice drop. Slope is at 8100 ft. in above treeline terrain. Located at the coordinates attached to this ob.

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