Wind Slab Avalanche on Elephant's Hump

Location Name: 
Elephant's Hump
Region: 
Carson Pass Area
Date and time of avalanche (best estimate if unknown): 
Mon, 01/02/2017 - 12:20
Location Map: 
United States
38° 41' 30.3864" N, 119° 58' 7.8096" 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
Observation made by: Forecaster
Avalanche Observations
Avalanche Type: 
Dry
Slab
Slope: 
38degrees
Trigger type: 
Skier
Crown Height: 
1 ft
Aspect: 
Northeast
Weak Layer: 
Old Snow
Avalanche Width: 
60ft.
Terrain: 
Near Treeline
Elevation: 
8 440ft.
Bed Surface: 
Old Snow
Avalanche Length: 
150ft.
Number of similar avalanches: 
1
More detailed information about the avalanche: 

An 8 to 16 inch deep wind slab avalanche released on a N-NE aspect as we were skinning up on a lower angle slope next to the wind slab. The slope cracked as I stepped onto the wind slab on the lower angle side near a small tree and the fracture propagated out into the steeper (37-39 degrees) wind-loaded slope causing the avalanche to release. The crown wrapped around the nose of the ridge and due to poor visibility and gale force winds we could not see the other side of the avalanche nor very far downslope. This avalanche failed on the near surface facets that existed on the snow surface yesterday. Ski kicks on other wind loaded test slopes with  30 to 34 degree slope angles caused some shooting cracks but did not release additional wind slabs. Gale force southwest wind transported this snow all day and wind-loading was occurring on any near or above treeline leeward slopes. In more sheltered areas, 4 to 5 inches of new snow existed by noon. In sheltered non-wind-affected areas, hand pits and snowpit tests showed poor bonding between the new snow and the old snow surface of near surface facets. The new snow easily broke away from the old snow surface. However, in these sheltered areas, the new snow had very limited slab characteristics. As more snow accumulates or as the new snow consolidates it could become more slab-like in these sheltered areas as well.

Photo 1 and 2: Crown of the avalanche from near the trigger point on a lower angle slope with some small trees.

Photo 3: Debris on the smaller flank of the avalanche. As it wraps around the corner the slope becomes larger and more open.

Photo 4: Shooting cracks on a wind-loaded slope triggered by a skier on the ridge. 

Avalanche Photos: 
Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
100% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Gale Force
Precipitation: 
Snow
Air temperature trend: 
Cooling
Wind Direction: 
Southwest
Accumulation rate: 
Less than 1 in. per hour
More detailed information about the weather: 

Strong gale force winds and blowing snow created white-out conditions on the ridgelines.