Avalanche on Tamarack Peak

Location Name: 
Tamarack Peak
Region: 
Mount Rose Area
Date and time of avalanche (best estimate if unknown): 
Wed, 12/29/2010 - 12:15
Location Map: 
United States
39° 18' 50.4792" N, 119° 55' 0.4404" 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,
Slope: 
38degrees
Trigger type: 
Skier
Crown Height: 
2 ft
Aspect: 
North
Weak Layer: 
Storm Snow
Avalanche Width: 
250ft.
Terrain: 
Near Treeline
Elevation: 
9 600ft.
Bed Surface: 
Storm Snow
Avalanche Length: 
400ft.
More detailed information about the avalanche: 

1.5' of new storm snow in the Tamarack Peak area today in protected areas.  Up to 2-3' + in wind loaded terrain at ridgelines.  Had shooting cracks, cracking, collapsing on the tour up close to ridgelines in wind loaded terrain.  Observed many small slab results within the upper snowpack from ski kicks and small cornice drops.  East of Prolitariate Bowl along the ridge, we had a substantial D2 slab avalanche from an intentional skier kicked cornice drop.  This cornice drop was approximately the size of a large washing machine and propagated both directions around 300' wide and ran full downslope to the flats around 400'.  Failure was within the storm snow around the time the storm went from warm to slightly colder temperatures.  This matched with stability test results on the side of this same slope, ECTP-28 Q1 and ECTP-23 Q1 both down approximately 2' on the weakness in the new storm snow.  Slope was north aspect, 9600', very wind loaded, 38-40 degrees quickly getting below 30 degrees and running into very low angle terrain.  The debri pile was 4-6' deep.  D2 avalanches can bury, injure, or kill a skier or rider.   

 

Photo#1: Avalanche from top view.  2-3' crown with some larger areas in the most wind loaded terrain.

Photo#2:Large shooting cracks propagated towards skiers left of path into less steep terrain, cracks went as far as I could see.

Photo#3:Another view showing bed surface and length of avalanche.

Photo#4: From debris pile looking up at crown, debris pile 4-6' deep

 

Avalanche: SS-R3-S-AC-D2-BP

There was some evidence of previous avalanche activity and cornice failures that were covered up by the storm snow in this area.

Avalanche Photos: 
Avalanche observation video: 

mt rose2010 12 29 007

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: 

Moderate to strong SW winds that were swirling around from all directions. Full white out blizzard conditions at times.