Large slab fracture. NE side of Castle Peak

Location Name: 
Castle Peak
Region: 
Donner Summit Area
Date and time of avalanche (best estimate if unknown): 
Mon, 02/21/2011 - 04:26
Location Map: 
United States
39° 22' 7.9536" N, 120° 21' 8.766" W
See map: Google Maps
US


Red Flags: 
Recent avalanche activity
Recent loading by new snow, wind, or rain
Obvious avalanche path
Observation made by: Public
Avalanche Observations
Avalanche Type: 
slab,
Slope: 
48degrees
Trigger type: 
Natural
Crown Height: 
5 ft
Aspect: 
East
Weak Layer: 
Storm Snow
Avalanche Width: 
250ft.
Terrain: 
Above Treeline
Elevation: 
8 600ft.
Bed Surface: 
Storm Snow
Avalanche Length: 
1 000ft.
More detailed information about the avalanche: 
Pic #1. Large slab fracture north of Castle peak, probably triggered from cornice blocks falling from above. The crown (4'-5') and debris form this slab release looked very fresh, it probably occurred over night prior to our arrival. Our vantage was from across the valley. Pic# 2. Naturally occurring slab release on the south side (north facing) ridge of Castle Pk (the area often skied). Crown height 8"/ width 40'/ run-out 500'. Pic# 3. Run-out of the same slide, looking up from below. Pic# 4. Skier cut slab release similar to the slide shown in the previous photos.
Avalanche Photos: 
Weather Observations
Blowing Snow: 
No
Air temperature: 
Below Freezing
Wind Speed: 
Calm
Precipitation: 
None
Air temperature trend: 
Static
Wind Direction: 
Northeast
Accumulation rate: 
None
More detailed information about the weather: 

The terrain facing N NW S SW was very wind affected by yesterdays winds. East facing slopes were wind loaded and heavily corniced.