Small Avalanche in WestFork cabin drainage

Location Name: 
South side of Westside cabin drainage
Region: 
Selkirk Mountains
Date and time of avalanche (best estimate if unknown): 
Sat, 02/16/2019 - 14:00
Location Map: 
United States
48° 51' 21.0888" N, 116° 45' 26.1972" W
See map: Google Maps
US


Red Flags: 
Whumphing noises, shooting cracks, or collapsing
Recent loading by new snow, wind, or rain
Observation made by: Public
Avalanche Observations
Avalanche Type: 
Slab
Slope: 
50degrees
Trigger type: 
Other - explain below
Crown Height: 
3 ft
Aspect: 
North
Weak Layer: 
Other - explain below
Avalanche Width: 
250ft.
Terrain: 
Above Treeline
Elevation: 
5 680ft.
Bed Surface: 
Old Snow
Avalanche Length: 
120ft.
More detailed information about the avalanche: 

While riding around a known rock bluff that usually slides naturally over waterfalls. After shutting off sleds we heard a pop up near the the slide zone where a 2-3ft storm slab broke loose sliding 150ft down the hill. Stopping in the trees below. After checking out what slide I went into the small slide to check out what it slide on. It appeared to have slide on a 6-9cm firm crust which appeared to be sun baked. What I found interesting below that layer was a crystal clear ice layer that was 2cm thick. Below the ice layer was very light density snow that bonded very well with the layers below.

Snowpit or crown profile photo or graph: 
Weather Observations
Blowing Snow: 
No
Cloud Cover: 
100% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Calm
Precipitation: 
None
Air temperature trend: 
Cooling
Wind Direction: 
Accumulation rate: 
None
More detailed information about the weather: