Natural avalance on Hidden Peak D2

Location Name: 
Hidden Peak
Region: 
West Shore Area
Date and time of avalanche (best estimate if unknown): 
Mon, 12/20/2010 - 13:30
Location Map: 
United States
38° 58' 40.5372" N, 120° 7' 39.522" 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: Forecaster
Avalanche Observations
Avalanche Type: 
dry,slab,
Slope: 
40degrees
Trigger type: 
Natural
Crown Height: 
Less than 1 ft
Aspect: 
East
Weak Layer: 
Storm Snow
Avalanche Width: 
200ft.
Terrain: 
Near Treeline
Elevation: 
9 000ft.
Bed Surface: 
Storm Snow
Avalanche Length: 
200ft.
Number of similar avalanches: 
2
More detailed information about the avalanche: 

Photo 1: Natural avalanche likely occurred less than 2 hours prior to arrival at 1:30 pm. Failure occurred on slightly higher density new snow over lower density new snow that likely formed with a couple degrees of daytime warming. Crown depth 15 cm.

Photo 2: Very easy to trigger additional small slab avalanches on adjacent slopes along the ridge just to the north of the natural avalanche location. ECTPV on crown with failure on column isolation.

Widespread sluffing in steep wind protected areas below treeline.

Snowpit or crown profile photo or graph: 
Avalanche Photos: 
Weather Observations
Blowing Snow: 
No
Cloud Cover: 
100% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Light
Precipitation: 
Snow
Air temperature trend: 
Warming
Wind Direction: 
Southwest
Accumulation rate: 
More detailed information about the weather: 

Snowfall rate of 0.5 to 1 inch per hour during most of the day.