Cornice collapse and rockfall on Donner Peak

Location Name: 
Donner Peak
Region: 
Donner Summit Area
Date and time of observation: 
Mon, 04/18/2011 - 19:00
Location Map: 
United States
39° 18' 44.2908" N, 120° 18' 55.4688" W
See map: Google Maps
US


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

Shin to knee deep wet snow existed on all aspects in the Donner Peak area this eveing. A ski cut on a SE aspect at 7200 ft. produced a small wet, loose sluff that only entrained the top 2-4 inches of wet snow. Some skier triggered roller balls also occurred in this area.

The rain also caused a large natural cornice failure and some natural rock fall on E-NE facing slopes on Donner Peak. When the large cornice pieces and the rocks hit the steep slopes below, they entrained some of the wet surface snow but did not cause any larger wet snow instabilities.

Photo 1: Natural cornice failure and debris

Photo 2: Rock fall and debris

Snowpack photos: 
Weather Observations
Blowing Snow: 
Cloud Cover: 
100% of the sky covered by clouds
Air temperature: 
Above Freezing
Wind Speed: 
Moderate
Precipitation: 
Rain
Air temperature trend: 
Cooling
Wind Direction: 
Southwest
Accumulation rate: 
Less than 1 in. per hour
More detailed information about the weather: