Shirley Canyon slide in the Silverado area

Location Name: 
Silverado @ Squaw Valley
Cabin Creek, Deep Creek, or Pole Creek Area
Date and time of avalanche (best estimate if unknown): 
Wed, 05/18/2011 - 15:30
Location Map: 
United States
39° 12' 2.3976" N, 120° 15' 25.632" W

Red Flags: 
Rapid warming
Obvious avalanche path

Observation made by: Public
Avalanche Observations
Avalanche Type: 
Trigger type: 
Weak Layer: 
Old Snow
Avalanche Width: 
Below Treeline
6 800ft.
Bed Surface: 
Storm Snow
Avalanche Length: 
Number of similar avalanches: 
Number of people caught: 
More detailed information about the avalanche: 

We started up Shirley canyon at 10am with the aim of reaching the top of Silverado by noon under overcast skies. It had snowed 6"-9" the previous night and the storm was just clearing. Numerous point releases all over squaw valley and the tram face were already present. The weather was overcast with intermittent snow but temps were sub 40 deg F when we headed out. Desite the number of point releases, we did not see any slab evidence and so we decided to head up Shirley canyon to ski silverado. It took us approximately 2.5 hours to the top. We skied 2 runs down with no instabilitily on the north facing slope we skied. At about noon, the sun broke through and it became quite hot, and snow quality deterioration was clear. We heard several small ice/snow releases through china wall on Silverado. The snow deterioration convinced us to head down. We headed down along the out of bounds line along skier's right of silverado. As we approached the steep portion of the lower bowl, we both commented that given the solar heating, slide possibility was high. We made our way down the run while I made cuts on my snowboard, releasing slabs with approximately 6" crests. We skied down through the pre-released area. We decided to cut right over an approximately 15 foot cliff-band, setting off wet-slabs as we went. My friend got a bit hot on the traverse and set of a 6" crown that was approx 10 feet wide and 6 feet down the hill. Despite the small crown, the heavy snow was enough to carry him over the 15 foot cliff and it carried him another 50+ yards beyond. He lost both skies, goggles, etc but was somehow unharmed. He was not burried, or hurt, and lucky to be just past the group of trees present, falling off the cleanest portion of the cliffband. On the skin out, dozens of new wet-slides were visible and the snow had changed from powder to sun-beat spring slush on all faces below 7000 feet.

Avalanche Photos: 
Weather Observations
Blowing Snow: 
Air temperature: 
Above Freezing
Wind Speed: 
Mixed rain and snow
Air temperature trend: 
Wind Direction: 
Accumulation rate: 
More detailed information about the weather: 

The sun cleared twice. Given that it was mid-may, it became incredibly hot when it cleared, but waves of clouds were moving in and out the entire time. It got warmer and warmer throughout the day. It cleared for approx. 1.5 hours around 2pm, and during that time it reached the mid-50's and the snow changed rapidly. When we were leaving a hail storm hit, with large hail on the roadway.