Huge Cornice Failure triggers medium size avalanche on Carson Pass - One Person Caught

Location Name: 
Frog Lake Cliffs
Carson Pass Area
Date and time of avalanche (best estimate if unknown): 
Mon, 03/28/2011 - 08:30
Location Map: 
United States
38° 41' 14.5896" N, 119° 58' 59.0268" W

Red Flags: 
Recent avalanche activity
Recent loading by new snow, wind, or rain
Obvious avalanche path

Observation made by: Public
Avalanche Observations
Avalanche Type: 
Trigger type: 
Other - explain below
Crown Height: 
4 ft
Weak Layer: 
Storm Snow
Avalanche Width: 
Near Treeline
8 900ft.
Bed Surface: 
Storm Snow
Avalanche Length: 
Number of people caught: 
More detailed information about the avalanche: 

After skiing and riding Elephants Back on Carson Pass at sunrise, 5 of us (3 skiers and 2 snowboarders) were headed down to the Red Lake parking lot to grab our car.  We were traversing across the flat ridgeline above Carson Pass looking for a good place to drop in.  On one section of ridgeline we were aware of a very large cornice.  We traversed about 30+ feet back from the ridge to avoid triggering an avalanche.  Apparently it wasn't far enough.  We were also staggered over 100 feet apart from one another practicing safe travel in avalanche terrain.  The last person in line was about a foot inside of the track set across the ridgeline.  Without warning over 100 feet of the ridgeline disappeared in front of us taking the last man in line with it.  The remaining 4 of us were about a foot away from being taken away ourselves.  The sound was equivalent to a freight train.  Chunks of snow larger than school buses barreled down the slope sliding for over 300 feet.  Amazingly, our friend wasn't buried and was uninjured.  All of us, very experienced skiers and snowboarders in backcountry terrain, agreed that it was the largest thing any of us had ever seen.  I am so happy everyone was alright.  It could have, and probably should have been, a much worse situation.

Additional comments after discussion between TNF/SAC forecaster and reporting party:

The weight of the cornice sections (which would be measured in tons) impacting the slope below triggered a slab avalanche with failure of the high density surface wind slab. The crown was approximately 2 feet tall on climber's left to 3-4 feet tall on climber's right side. The avalanche debris travelled approximately 75 feet down slope while the cornice debris traveled approximately 300' feet down slope sliding on top of the high density snow surface. Most of the debris visible in the photos are from the cornice rather than from the hard slab avalanche.

Avalanche Photos: 
Weather Observations
Blowing Snow: 
Cloud Cover: 
Air temperature: 
Below Freezing
Wind Speed: 
Air temperature trend: 
Wind Direction: 
Accumulation rate: 
More detailed information about the weather: