6-10'' New Snow and Reactive Windslabs on Andesite Peak

Location Name: 
Andesite Peak
Region: 
Donner Summit Area
Date and time of avalanche (best estimate if unknown): 
Wed, 03/06/2013 - 08:00
Location Map: 
United States
39° 21' 3.978" N, 120° 21' 59.8572" 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,loose,
Trigger type: 
Skier
More detailed information about the avalanche: 

6-10'' of new storm snow in the Andesite/Castle Peak area by early morning.  Lots of signs of snowpack instabilities while touring up with cracking around skis and long shooting cracks in wind loaded terrain.  Strong to gale SW winds were moving large amounts of snow with plenty of snow still available for transport.  Wind slabs failed easily in the most wind loaded and steep terrain with ski kicks.  Below treeline in protected terrain there were no signs of storm slab weaknesses but loose dry avalanches (sluffing) were common in steeper protected terrain.

 

Photos#1,#2, #3:  Cracking around skis and large shooting cracks from Castle Pass up to Andesite Peak, 7600'-8200', N-E aspects.

Photo#4:  Small wind slab triggered by a ski kick on the North shoulder of Andesite Peak, 8100', East aspect, 35-40 degree slope.  Crown up to 1.5' deep.  Same location as Video #2.

Photos#5,#6,#7:  D2 wind slab avalanche just below (East) of Andesite Summit in below treeline but exposed terrain - 8000', NE/E aspect, 40 degree starting zone.  Crown ranged from 6'' to 2' deep, 125' wide x 250' long.  Debris was 2-3' deep into the trees.  N 39.35060, W 120.36525 

Video#1:  ECTP-24 down 1.5' on wind slab density change.  8100' , NE/E aspect, 30 degree slope.

Video#2:  Skier triggered wind slab with a ski kick off the summit of Andesite Peak.  East aspect, 35-40 degree slope, 8100'.

Avalanche Photos: 
Avalanche observation video: 

AndesitePeak2013-3-6 013

AndesitePeak2013-3-6 009

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

Moderate snow bands moving through this area in the morning with a couple breaks in between.  Strong SW winds with gusts into the gale range making for white out conditions.