Fractured wind slab on the back side of Castle Peak.

Location Name: 
Castle Peak
Region: 
Donner Summit Area
Date and time of avalanche (best estimate if unknown): 
Fri, 04/02/2010 - 10:00
Location Map: 
United States
39° 21' 45.954" N, 120° 20' 32.0316" 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
Obvious avalanche path
Observation made by: Public
Avalanche Observations
Avalanche Type: 
slab,
Slope: 
36degrees
Trigger type: 
Natural
Crown Height: 
1 ft
Aspect: 
North
Weak Layer: 
Storm Snow
Avalanche Width: 
150ft.
Terrain: 
Above Treeline
Elevation: 
8 600ft.
Bed Surface: 
Old Snow
Avalanche Length: 
350ft.
More detailed information about the avalanche: 

Naturally occuring slab fracture likely triggerd from conice failure at the top of the bowl. The bed depth was 14"-16" and 150' wide/ 200' long, some large blocks ran out an additional 100' or so. There was no additional propogation visable down slope. The entire ridge was freshly windloaded by the approaching storm. Several areas produced multiple shooting cracks, fractures and settling under body weight, though I kick tested two areas and could not get the cornices to break free. 12:30 pm

(the photo was taken with my crappy camera phone)

Note the diagonal cracks in the fore ground (left side of photo) eminating from slide area. This is the middle bowl that is often skied.

Avalanche Photos: 
Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
100% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Strong
Precipitation: 
Snow
Air temperature trend: 
Cooling
Wind Direction: 
Accumulation rate: 
Greater than 1 in. per hour
More detailed information about the weather: 

Estimated wind speed on the ridge at 12:00 noon was 20-30 mph, gusts 40-50 mph. Blowing out of the West and South West. Snow accumulation was a little more than 1"/ hour.