Avalanche on the far east ridge of Tamarack Peak

Location Name: 
Far East Ridge of Tamarack Peak
Region: 
Mount Rose Area
Date and time of avalanche (best estimate if unknown): 
Wed, 01/13/2010 - 12:00
Location Map: 
United States
39° 18' 46.5048" N, 119° 54' 39.9384" 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: 
38degrees
Trigger type: 
Skier
Crown Height: 
3 ft
Aspect: 
Northeast
Weak Layer: 
Other
Avalanche Width: 
150ft.
Terrain: 
Above Treeline
Elevation: 
9 200ft.
Bed Surface: 
Other - explain below
Avalanche Length: 
300ft.
Number of similar avalanches: 
1
More detailed information about the avalanche: 

Several layers existed with in the snow that has fallen in the last 36 hours. The following snow stratigraphy was observered in the Mt. Rose area today: 4f wind slab (today and last night), F new snow with a graupel layer at the bottom (last night), 4f wind slab (formed yesterday during the day), F new snow (from Mon. night), then the old crust. The thickness ranges between 5-15 cm on each layer in most places depending on wind-loading. Easy shears at each of the density changes. Several of these wind slabs near and above treeline were active in the Mt. Rose area today.

The attached video shows a  2.5-3ft deep crown on the east ridge of Tamarack Peak that was triggerred by stomping on the slope above the slide. It is a 38 degree, NE (22 degrees) facing slope. It started as a failure near the bottom of the new snow just above old surface crust then stepped down about one more inch to take just the crust with it after about 1.5 ft of travel.  Small near crust facets were the failure layer under the old snow surface crust.  This slide took some force to initiate but propagated across the whole slope very quickly once the right spot was triggered. 

Photo#1 is of a 37 degree, NE (22 degrees) facing test slope that was also skier triggered at about 8900'. This test slopes failed on a density change in the new snow. It failed about 1 hr before the skier-triggered slide in the video.

Photo#2: Above location, looking down at first avalanche path to the debris field.

Avalanche Photos: 
Avalanche observation video: 

Skier-triggered avalanche on the far east ridge of Tamarack Peak.

Weather Observations
Blowing Snow: 
Yes
Air temperature: 
Below Freezing
Wind Speed: 
Moderate
Precipitation: 
None
Air temperature trend: 
Static
Wind Direction: 
Southwest
Accumulation rate: 
None
More detailed information about the weather: