Natural Avalanche Tahoe Donner

Location Name: 
Bowl between Drifter and Hawk's Peak
Region: 
Donner Summit Area
Date and time of avalanche (best estimate if unknown): 
Sat, 03/17/2012 - 11:00
Location Map: 
United States
39° 21' 26.1468" N, 120° 17' 0.9564" W
See map: Google Maps
US


Red Flags: 
Obvious avalanche path
Observation made by: Public
Avalanche Observations
Avalanche Type: 
dry,slab,
Slope: 
35degrees
Trigger type: 
Natural
Crown Height: 
10 ft
Aspect: 
North
Avalanche Width: 
200ft.
Terrain: 
Below Treeline
Elevation: 
7 500ft.
Bed Surface: 
Old Snow
Avalanche Length: 
300ft.
More detailed information about the avalanche: 

 As described in your forecast, this avalanche went down to an old base layer at least 6' down but probably more.  This is an area where there have been frequent slides.  Usually two types; wind slabs breaking off the north-south ridge, and avalanches caused by a convex rollover on the north slope.  I always give this slope some bearth unless I'm 100% certain that it's safe.

We dug a pit at Drifter peak and found only moderate weakness (isolated column, 3 tap from wrist, slight slippage about 10" down) in the top layer.  Skied several runs off Drifter and 1 run down Hawk's peak.

Avalanche Photos: 
Weather Observations
Air temperature: 
Below Freezing
Wind Speed: 
Calm
Precipitation: 
Air temperature trend: 
Static
Wind Direction: 
Southwest
Accumulation rate: 
More detailed information about the weather: 

 Not much accumulation if any during the day.  Light snowfall late in the afternoon.  This slide was likely caused by the previous day's 3/16 snowfall (probably a heavy 2' with a light 2' overnight)