Wind slabs at Carson Pass

Location Name: 
Elephant's Hump
Region: 
Carson Pass Area
Date and time of observation: 
Mon, 11/19/2012 - 10:00
Location Map: 
United States
38° 41' 13.668" N, 119° 58' 49.152" W
See map: Google Maps
US


Red Flags: 
Recent avalanche activity
Recent loading by new snow, wind, or rain
Rapid warming
Obvious avalanche path
Observation made by: Professional Observer
Snowpit Observations
More detailed information about the snowpack: 

Pic: Cornices have developed along Frog Lake Ridge. A piece of this cornice failed sometime late yesterday and produced a D1 R1 that propagated 30ft to either side of where the cornice fell.

Video 1: Taken at 38.687754,-119.98332. 2nd of 2 ECTs to fail and propagate on the 21st tap on a storm snow instability below supportive wind slab and above recent rain layer that acted as bed surface in a human triggered avalanche yesterday. Hand shears and shovel shears on remaining snow above rain layer were Moderate with Q2 and Q3 shear quality.

Video 2: Taken at 38.68713, -119.98032, about 50ft adjacent to the crown from yesterday's avalanche. Exact same results as previous ECTs, including shear tests on remaining snow above rain layer.

In general, this south side of Carson Pass was quite wind effected, with windward slopes stripped down to the recent rain layer, and lee slopes wind loaded with supportive wind slab. Ski pen on this wind slab averaged 5-10cm, while boot pen was 40cm and greater. On steep, unsupported pockets where the density change noted in above videos was close to the surface, I was able to kick off small chunks of wind slab. Elsewhere, the wind slab was too well supported to produce results.

Recent rain layer was observed to my high point of 9400ft. HS in start zones on lee slopes ~120cm.

Snowpack photos: 
Weather Observations
Blowing Snow: 
Yes
Air temperature: 
Below Freezing
Wind Speed: 
Moderate
Precipitation: 
None
Air temperature trend: 
Warming
Wind Direction: 
South
Accumulation rate: 
None
More detailed information about the weather: 

Rapid warming observed shortly before 11am.