Shallow wind slab human triggered avalanche with step down within storm snow on Silver Pk

Location Name: 
Silver Peak
Region: 
Cabin Creek, Deep Creek, or Pole Creek Area
Date and time of avalanche (best estimate if unknown): 
Sat, 03/19/2011 - 15:30
Location Map: 
United States
39° 13' 24.636" N, 120° 14' 34.0296" W
See map: Google Maps
US


Red Flags: 
Recent loading by new snow, wind, or rain
Obvious avalanche path
Observation made by: Forecaster
Avalanche Observations
Avalanche Type: 
dry,slab,
Slope: 
38degrees
Trigger type: 
Skier
Crown Height: 
2 ft
Aspect: 
North
Weak Layer: 
Storm Snow
Avalanche Width: 
150ft.
Terrain: 
Near Treeline
Elevation: 
7 930ft.
Bed Surface: 
Storm Snow
Avalanche Length: 
75ft.
More detailed information about the avalanche: 

Intentional remotely skier triggered avalanche from top of ridge by pictured skier at pictured location. Remote trigger from 15 feet away on upper edge of wind loaded section. Avalanche initiated on 15cm thick wind slab 4F+ hard at top decreasing to 4F hard at bottom of slab. The bed surface was F hard storm snow. The avalanche stepped down to 60cm a short ways downslope, still within the storm snow. Surface wind slab represented 20 to 25% of the total new snow in this area.

Shooting cracks very limited to directly wind loaded areas near cornice features only in this entire area.

Evidence of one very small natural from last night along the same ridge, just to the east of this skier triggered avalanche. Otherwise no other evidence of natural avalanche activity from yesterday/last night.

Sluffing of top 5cm of storm snow in response to ski cuts in steep wind protected areas below treeline. No other evidence of instability noted while on tour in below below treeline areas today.

Overall the snowpack was very right side up with significant settlement noted during the afternoon. Settlement cones with seperation up to 5cm observed around trees at 7,700' on N aspects at 3pm.

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: 
Static
Wind Direction: 
Southwest
Accumulation rate: 
Less than 1 in. per hour
More detailed information about the weather: 

Snow amounts during the morning hours exceeded forecast amounts, but did not effect stability.