Small Wind-Slab Avalanche - Dick's Peak - 1.31.10

Location Name: 
Dick's Peak
Region: 
Desolation Wilderness Area (including Emerald Bay)
Date and time of avalanche (best estimate if unknown): 
Sun, 01/31/2010 - 11:00
Location Map: 
United States
38° 54' 23.7492" N, 120° 8' 36.6828" W
See map: Google Maps
US


Red Flags: 
Recent loading by new snow, wind, or rain
Observation made by: Public
Avalanche Observations
Avalanche Type: 
dry,slab,
Slope: 
35degrees
Trigger type: 
Skier
Crown Height: 
Less than 1 ft
Aspect: 
Northwest
Weak Layer: 
Other
Avalanche Width: 
50ft.
Terrain: 
Above Treeline
Elevation: 
8 700ft.
Bed Surface: 
Other - explain below
Avalanche Length: 
20ft.
Number of similar avalanches: 
2
More detailed information about the avalanche: 

On 1.31.10 there were several small wind-slab avalanches set off at Dick's Peak.  When skinning up on both 1.30.10 and 1.31.10, both quick pole tests and hand-shear tests revealed a slightly inverted snowpack, with medium density wind slabs sitting on lower density snow.  Throughout informal tests, the wind slabs were generally 20 cms thick.   Conditions were generally variable at Dick's Peak, with wind-slabs and wind-affected snow, to softer snow in true North aspects.  Compare to the N-aspects of Jannie's Ridge, which was holding soft, wintery snow with no evidence of wind loading or instability.

On the NW ridge of Dick's Peak, there was visible wind loading occurring due to strong ridge-top winds.  We dropped 2 cornices with no results.

 

The photos above were from an approximately 50ft wide, 15ft down slope wind slab slide.  It was skier triggered and broke at my feet at near thinner areas of the snowpack (rocks, etc...).  The crown was approximately 6 inches tall and the slab blocks after breaking only slide 30-40 feet, at a very slow speed.  I was able to let the slab initiate, and then slowly ski behind it.

My partner also set off a similar small, near-surface wind slab at the same aspect and slope, but near ridge line (approximately 9,000 ft).  That wind-slab had a smaller crown and did not travel far.  

Finally, we witnessed a third party initiate a similar small, near-surface wind slab as the above (my partner's).

In all cases, the wind-slabs appeared to initiate at the skier and down slope.

Avalanche Photos: 
Weather Observations
Blowing Snow: 
Yes
Air temperature: 
Above Freezing
Wind Speed: 
Strong
Precipitation: 
None
Air temperature trend: 
Warming
Wind Direction: 
South
Accumulation rate: 
None
More detailed information about the weather: 

 On the skin in Dick's bowl, there were moderate S-winds that were transporting surface snow at a light rate.  Ridge top winds were strong and steady at approximately 30 mph (with higher gusts).