Small natural avalanche

Location Name: 
Lake Marry west side Donner Pass
Region: 
Donner Summit Area
Date and time of avalanche (best estimate if unknown): 
Sun, 12/26/2010 - 03:00
Location Map: 
United States
39° 18' 46.6236" N, 120° 19' 50.4372" W
See map: Google Maps
US


Red Flags: 
Recent avalanche activity
Recent loading by new snow, wind, or rain
Terrain Trap
Observation made by: Public
Avalanche Observations
Avalanche Type: 
dry,slab,
Slope: 
45degrees
Trigger type: 
Natural
Crown Height: 
1 ft
Aspect: 
East
Weak Layer: 
Old Snow
Avalanche Width: 
50ft.
Terrain: 
Below Treeline
Elevation: 
7 020ft.
Bed Surface: 
Old Snow
Avalanche Length: 
60ft.
More detailed information about the avalanche: 

The slide  is on a 45 degree east facing slope.  The total height of the hill is only 60-70' tall but it has everything needed to form a dangerous avalanche. The lake at the bottom is a very effective terrain trap. Notice the photo with the large crack in the deposits as the weight of the deposits sunk into the lake. There is a convex rollover mid way and at the top often a cornice.  Last time I saw  this slope slide, I was helping respond to an avalanche accident where 4 people were caught and buried  4' under for four hours.  There was one fatality from hypothermia. Ironically our Avi 1 class was going out to see the slope.  I had used the case history in our class to illustrate some points the day before. Both times very strong to extreem  W-SW winds helped to formed the windslabs that slid.

Avalanche Photos: 
Weather Observations
Blowing Snow: 
No
Cloud Cover: 
Clear
Air temperature: 
Above Freezing
Wind Speed: 
Calm
Precipitation: 
None
Air temperature trend: 
Cooling
Wind Direction: 
Accumulation rate: 
None
More detailed information about the weather: