Heavy Wet New Snow and Windslabs on Andesite Peak

Location Name: 
Andesite Peak
Region: 
Donner Summit Area
Date and time of avalanche (best estimate if unknown): 
Wed, 03/20/2013 - 09:30
Location Map: 
United States
39° 21' 2.448" N, 120° 22' 0.6456" 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
Observation made by: Professional Observer
Avalanche Observations
Avalanche Type: 
dry,slab,
More detailed information about the avalanche: 

6-8'' of new, wet, heavy snow in the Castle Peak/Andesite Peak area in the early morning with up to 1.5' of wind drifted snow in the most wind loaded areas.  Newly formed wind slabs were very reactive with ski kicks and while approaching newly formed cornices.  Most of these wind slabs were 6-8'' with a couple in the most wind loaded areas being up to 1'.  In steeper terrain, these wind slabs propagated efficiently and ran full path.   The old snow surface and old snow below was moist for at least 1' deep on the East aspects that I observed.  

 

Photo#1:  Small natural wind slab avalanche occuring in the early morning off a small cornice failure off of Andesite Peak.  8200', East aspect, 32-36 degrees, up to 1' deep. 

Photo#2 and #3:  Skier triggered wind slab on the shoulder of Andesite Peak.  East aspect, 35 degrees, 8100', 6-8'' deep.

Photo#4 and #5:  2 separate wind slab avalanches skier triggered on convex rollovers, both East aspects 35-40 degrees, 8000', 4-8'' deep.

 

Video#1:  ECTP-16 down 1' on newly formed windslab.  This ECT done adjacent to a small natural avalanche off of Andesite Peak-8200', East aspect, 32 degree slope.

Video #2:  Skier triggered windslab avalanche from cornice failure while approaching lip.  8000', NE aspect, 40 degree slope, 6-8'' crown.

Avalanche Photos: 
Avalanche observation video: 

AndesitePeak2013-3-20 010

AndesitePeak2013-3-20 014

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

Snow level at 6500' in the early morning and remaining consistent throughout the morning.  Snowfall rate just below 1'' per hour.