Natural avalanche cycle in Deep Creek (Small D1 avalanches)

Location Name: 
Deep Creek
Region: 
Cabin Creek, Deep Creek, or Pole Creek Area
Date and time of avalanche (best estimate if unknown): 
Mon, 02/27/2012 - 10:30
Location Map: 
United States
39° 14' 43.836" N, 120° 14' 16.044" 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: 
38degrees
Trigger type: 
Natural
Crown Height: 
Less than 1 ft
Aspect: 
North
Weak Layer: 
Storm Snow
Avalanche Width: 
40ft.
Terrain: 
Below Treeline
Elevation: 
7 720ft.
Bed Surface: 
Storm Snow
Avalanche Length: 
10ft.
Number of similar avalanches: 
More than 10
More detailed information about the avalanche: 

A natural avalanche cycle occurred around 10-11am on NW-N-NE aspects near and below treeline in this area. Snowpack failure occurred within the storm snow on a thin layer of lightly rimed new snow grains 3 cm above the old/new snow interface. Slopes steeper than 35 degrees had soft slab D1 natural avalanches with crown depth of 12cm. Many slopes between 30 and 35 degree slope angle had widespread "en echalon" cracking.

Photo: Small natural avalanche at noted lat/long. At the time of the photo, the cracks, crown, and debris were covered by about 7 cm of new snow. Close inspection reveals "en echalon" cracking above the crown and debris below.

Avalanche Photos: 
Weather Observations
Blowing Snow: 
No
Cloud Cover: 
100% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Calm
Precipitation: 
Snow
Air temperature trend: 
Static
Wind Direction: 
Accumulation rate: 
Greater than 1 in. per hour
More detailed information about the weather: 

Snowfall rates at 2+ inches per hour for most of the day.