Donner Summit Avalanche Activity

Location Name: 
Donner Summit
Region: 
Donner Summit Area
Date and time of avalanche (best estimate if unknown): 
Sat, 03/17/2012 - 08:00
Location Map: 
United States
39° 18' 40.0788" N, 120° 18' 48.9024" W
See map: Google Maps
US


Red Flags: 
Recent avalanche activity
Recent loading by new snow, wind, or rain
Observation made by: Professional Observer
Avalanche Observations
Avalanche Type: 
dry,slab,loose,
Trigger type: 
Natural
More detailed information about the avalanche: 

Many recent natural avalanches observed today in the Donner Summit area.  Most occurred during the storm and were slightly covered up by new snow.  All were NE-NW aspects, 35-45 degrees, and in heavily wind loaded terrain and some had a cornice failure as the trigger.  A test pit dug on a N aspect, 7800' showed 3.5' of snow on top of a rain crust that was still moist.  The persistent weak layer is over 6' deep and was felt with a probe.  The storm snow had a distinct density change that was reactive to CT's but not showing any signs of propagation.

Photo #1: North face of Donner Peak, 7600'.  Large amount of debris on the apron runout below the train tunnels.  The crown was covered up by storm snow but could be made out in spots.  200-250' wide and running just under 1000'.  Many dry loose avalanches on this north face as well.

Photo #2:  The "Poop Chute" on Donner Summit.  NW aspect.  Avalanche debris on the apron covered up by new snow.

Photo #3:  Sierra Crest looking S-SE from Mt. Lincoln.  Many natural cornice failures in this highly wind loaded terrain with some small slab avalanche releases.  NE-E aspects.

Avalanche Photos: 
Weather Observations
Cloud Cover: 
25% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Light
Precipitation: 
None
Air temperature trend: 
Static
Wind Direction: 
Southwest
Accumulation rate: 
None
More detailed information about the weather: 

Partly to mostly sunny day up on Donner Summit.  Light winds from the SW throughout the day.  Clouds increased by 3pm with some cooling and it began snowing by 4pm.