Remotely-triggered slide under Grouse Rock

Location Name: 
E-SE gully under Grouse Rock
Region: 
Blackwood Canyon or Ward Canyon Area
Date and time of avalanche (best estimate if unknown): 
Wed, 11/23/2016 - 08:00
Location Map: 
United States
39° 8' 0.4164" N, 120° 14' 25.1484" W
See map: Google Maps
US


Red Flags: 
Recent loading by new snow, wind, or rain
Observation made by: Public
Avalanche Observations
Avalanche Type: 
Slab
Trigger type: 
Skier
Crown Height: 
Less than 1 ft
Aspect: 
Northeast
Weak Layer: 
Unknown
Avalanche Width: 
30ft.
Terrain: 
Near Treeline
Elevation: 
8 000ft.
Bed Surface: 
Unknown
More detailed information about the avalanche: 

Skiied Grouse Rock this morning.  Wind slab was apparent near summit, with some fracturing apparent in the skin track, but no propagation observed.  'Stomp Tests' on convext test slopes produced no movement.  On our second lap, after finding stable conditions on the E-NE side of the ridge, we approached the E-SE gully that we'd passed on the way up.  I descended first while my partner observed from above.  Made a few turns in the gut, before cutting left to an island of safety at the gully's edge.  I turned around to see the crown pictured on the right side (more northern aspect) of the gully, and debris moving slowly down-slope.  The slab that released was several meters away from my own ski tracks, on a rocky convex roll-over.  Debris slid about 100 meters down-slope.  My partner and I cut left (north) out of the gully and descended safely along the ridgeline.  No one was injured.

Avalanche Photos: 
Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
75% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Moderate
Precipitation: 
Snow
Air temperature trend: 
Warming
Wind Direction: 
Southeast
Accumulation rate: 
Less than 1 in. per hour