Natural Avalanche Andesite Ridge

Location Name: 
Lower Andesite Ridge
Region: 
Donner Summit Area
Date and time of avalanche (best estimate if unknown): 
Wed, 01/24/2018 - 11:00
Location Map: 
United States
39° 20' 31.1928" N, 120° 21' 13.9824" W
See map: Google Maps
US


Red Flags: 
Recent avalanche activity
Recent loading by new snow, wind, or rain
Observation made by: Educator at Tahoe Mountain School
Avalanche Observations
Avalanche Type: 
Slab
Trigger type: 
Natural Cornice Collapse
Crown Height: 
Less than 1 ft
Aspect: 
Northeast
Weak Layer: 
New/old snow interface
Avalanche Width: 
40ft.
Terrain: 
Near Treeline
Elevation: 
7 500ft.
Bed Surface: 
Storm Snow
Avalanche Length: 
30ft.
Number of people caught: 
0
Number of partial burials: 
0
Number of full burials: 
0
More detailed information about the avalanche: 

Today at 11:00, found what appeared to be a natural avalanche at the most southern point on Andesite Ridge. D1, about 40 ft accross and about 15-20 ft in lenght. Occured right under the ridge,  at 7500'  on a NE aspect. Appeared to be recent, possibly from the early morning hours of 1/25. Hard to say exacty what triggered the windslab, if it released from rapid wind loading, or more likely that part of the cornice above broke and triggered it. This was the only obvious sign of instibility observed on this short tour despite over 12" of storm snow, consistent snow fall (it snowed around 2 " during the 3 hours out), and wind loading above treeline.

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: 
Static
Wind Direction: 
Southwest
Accumulation rate: 
Less than 1 in. per hour
More detailed information about the weather: