Donner Summit Observations

Location Name: 
Donner Summit
Region: 
Donner Summit Area
Date and time of observation: 
Thu, 03/03/2011 - 13:30
Location Map: 
United States
39° 18' 27.2592" N, 120° 19' 8.6304" 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: 

Lots of things going on in the upper snowpack from the last series of small, warm storms with heavy wind loading.  The most reactive layer was down 12-14'' on a storm snow instability that was showing hard results from the ECT and moderate results from the CT.  This layer was thought to be the one reactive from cornice drops and the recent human triggered avalanches in the area.  Below this layer was a 3'' thick graupel layer that was reactive to hard CT results but not reactive to ECT's and did not indicate propagation was likely with the PST.  Solar aspects had roller ball and point release activity from the morning/midday sun, temps cooled off with increased cloud cover in the afternoon.  Stability did seem to be improving throughout the day with much harder results from ski cuts, ski kicks and cornice drops.

 

Photo#1:  Large cornice release on Wildflower Ridge, 7800' N aspect, appeared to be very resent and covered up some ski tracks below.  Consistent easy cornice releases from ski kicks some resulting in propagation on the slope below.

Photo#2:  Natural cornice failures and slab failures on the east face of Mt. Judah.  Summit chair was closed and control work had not yet been done.  The largest slab ran to the flats at the bottom of the path.

Photo#3:  Witnessed at 1pm, small slab triggered by snowboarder approaching slope, 7400' NW aspect-just north of Poop Chute.

Photo #4:  Natural avalanche, N side Donner Peak.  Slightly covered up with new snow probably occured early morning hours.

Video#1:  ECTP-21 Q1 2x down 14'' on storm snow instability.

Video#2:  PST 65/100 END down 18'' on 3'' graupel layer.

Snowpack photos: 
Snowpit videos (tests, etc): 

donnersummit2011 3 3 006

donnersummit2011 3 3 007

Weather Observations
Blowing Snow: 
Yes
Air temperature: 
Below Freezing
Wind Speed: 
Light
Precipitation: 
None
Air temperature trend: 
Warming
Wind Direction: 
Southwest
Accumulation rate: 
More detailed information about the weather: 

The sun was strong briefly midday before clouds came back in and covered 75% of the sky.  Winds were light out of the SW moving light amounts of snow only in the most wind prone terrain.