Instability on Donner Summit

Location Name: 
Donner Summit
Region: 
Donner Summit Area
Date and time of observation: 
Tue, 12/28/2010 - 13:00
Location Map: 
United States
39° 18' 28.0368" N, 120° 19' 9.2964" W
See map: Google Maps
US


Red Flags: 
Recent avalanche activity
Whumphing noises, shooting cracks, or collapsing
Recent loading by new snow, wind, or rain
Observation made by: Professional Observer
Snowpit Observations
More detailed information about the snowpack: 

Small windslab forming from last night into today in highly wind loaded terrain about 4-6'' thick. This windslab was mainly formed by the moderate SW winds creating a denser windslab on top of the less dense old snow surface. Temps were warming throughout the morning with the rain level around 7000'. Cornice drops, ski kicks, and ski cuts all produced easy failure of the wind slab in highly wind loaded terrain. Although small, these windslabs propagated wide and had good downhill runs. The rain level seemed to remain consistent around 7000' into the early afternoon. Visibility was very limited with flat light conditions.

Photo#1: Small slab failure from a ski cut. 7800', north aspect 40 degree slope in wind loaded terrian.
Photo#2: Close up view of wind slab crown line, 4-6'' thick, 1F hardness.

Snowpack photos: 
Snowpit videos (tests, etc): 

donnersummit2010 12 28 007

donnersummit2010 12 28 006

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