Surface "sluffing" on the backside of Castle Peak.

Location Name: 
Castle Peak
Region: 
Donner Summit Area
Date and time of avalanche (best estimate if unknown): 
Wed, 12/15/2010 - 12:00
Location Map: 
United States
39° 21' 56.916" N, 120° 20' 43.9476" W
See map: Google Maps
US


Red Flags: 
Recent avalanche activity
Recent loading by new snow, wind, or rain
Obvious avalanche path
Terrain Trap
Observation made by: Public
Avalanche Observations
Avalanche Type: 
dry,
Slope: 
35degrees
Trigger type: 
Natural
Crown Height: 
1 ft
Aspect: 
North
Weak Layer: 
Old Snow
Avalanche Width: 
60ft.
Terrain: 
Above Treeline
Elevation: 
8 300ft.
Bed Surface: 
Old Snow
Avalanche Length: 
1 200ft.
Number of similar avalanches: 
More than 10
More detailed information about the avalanche: 
Many loose point sluffs (natural triggerd) running several hundred yards were observed upon arriving in the morning. We layed the first tracks in the area since the last storm. On steeper aspects 35-40 degrees, 10"-12" of light sugary (unconsolidated) snow would easily release under foot. Though the runouts were long, the sliding snow was isolated to troughs and gullys. No evidence of propagation was observed. WE skied 5 laps, sampling much of the terrain on the back side of Castle. The snow pack seemed to consolidate and tighten up as the day progressed. The old rain crust layer was noticeable on all aspects. The new snow surface was blanketed with plate crystals 2-4 cm in diameter.
Avalanche Photos: 
Weather Observations
Blowing Snow: 
No
Cloud Cover: 
Clear
Air temperature: 
Below Freezing
Wind Speed: 
Calm
Precipitation: 
None
Air temperature trend: 
Static
Wind Direction: 
Accumulation rate: 
More detailed information about the weather: 

Clean and calm in the morning. Light wind midday. Below freezing