Windslabs on Donner Summit

Location Name: 
Mt. Judah Area
Region: 
Donner Summit Area
Date and time of observation: 
Mon, 03/07/2011 - 12:00
Location Map: 
United States
39° 18' 27.4968" N, 120° 19' 7.7052" 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: 

Dense heavy storm snow with varying degrees of wind effect in the Donner Summit area today.  The rain event on Sunday during the warmest part of the day formed a 2cm rain crust observed up to 8000'.  Consistent cracking and shooting cracks in wind loaded terrain, cornices were very fragile and easy to ski kick off.  It appeared that many steeper slopes had avalanched during the storm, probably during the rain event, then had been partially covered up by new snow.  The 3/6 rain crust showed the most consistent failures with ski cuts and cornice drops and matched well with formal stability tests.

 

Photo#1:  Skier triggered windslab on Wildflower Ridge @ 11am, north aspect, 7800'.  Slab depth up to 1.5' sliding on the pencil hard rain crust that formed on Sunday during the rain event at higher elevations.

Photo#2:  Skier triggered windslab on Wildflower Ridge @ 11:30am.

Photo#3:  Roller balls and small point releases on east aspects from brief amounts of sun and warming, around 7000'.

Video#1:  ECTP-2 Q2 down 40cm just above 3/6 rain crust.

Video#2:  PST 25/100 END down 40cm just above 3/6 rain crust

Video#3:  Showing wind loading during midday hours.

Snowpack photos: 
Snowpit videos (tests, etc): 

donnersummit2011 3 7 018

donnersummit2011 3 7 019

donnersummit2011 3 7 020

Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
75% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Moderate
Precipitation: 
None
Air temperature trend: 
Warming
Wind Direction: 
Southwest
Accumulation rate: 
More detailed information about the weather: 

Mostly cloudy with brief periods of intense sun.  SW moderate winds consistent throughout the day.