Small avalanche on Tram Ridge

Location Name: 
Tram Ridge / Shirley canyon
Region: 
Cabin Creek, Deep Creek, or Pole Creek Area
Date and time of avalanche (best estimate if unknown): 
Sat, 02/18/2017 - 13:45
Location Map: 
United States
39° 11' 56.1732" N, 120° 15' 5.0832" W
See map: Google Maps
US


Red Flags: 
Recent loading by new snow, wind, or rain
Obvious avalanche path
Observation made by: Guide at Alpenglow Expeditions
Avalanche Observations
Avalanche Type: 
Wet
Slab
Slope: 
40degrees
Trigger type: 
Skier
Crown Height: 
Less than 1 ft
Aspect: 
North
Weak Layer: 
Storm Snow
Avalanche Width: 
30ft.
Terrain: 
Below Treeline
Elevation: 
7 200ft.
Bed Surface: 
Storm Snow
Avalanche Length: 
200ft.
Number of people caught: 
0
Number of partial burials: 
0
Number of full burials: 
0
More detailed information about the avalanche: 

Skiing the Tram Ridge zone this afternoon we noticed a couple things going on with the snowpack. Near the ridgeline in the wind loaded zone, the small, stiff windslab was sitting on a layer of very low density snow. Hand shears produced clean, easy failures at this layer, but the slab was quite stubborn, with no shooting cracks or other signs of instability. Lower down an agressive ski cut on a small convex feature was able to produce a slab avalanche that ran roughly 200' to the bench below. The upper snowpack was wet and heavy, and this was well below ridgeline in a sheltered area. 

Photo #1- Easy hand shear of small windslab near ridgeline

Photo #2- Lower density layer below windslab

Photo #3- Small avalanche intentionally triggered by ski cut

Avalanche Photos: 
Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
100% of the sky covered by clouds
Air temperature: 
Above Freezing
Wind Speed: 
Moderate
Precipitation: 
Air temperature trend: 
Warming
Wind Direction: 
Southwest
Accumulation rate: 
More detailed information about the weather: