Negro Canyon Observations

Location Name: 
Negro Canyon
Region: 
Donner Summit Area
Date and time of observation: 
Tue, 12/21/2010 - 10:00
Location Map: 
United States
39° 20' 48.516" N, 120° 17' 45.8232" 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: 
4-6'' of storm snow from Monday sitting on top of the 12/19 rain crust. This rain crust is mostly ski supportive at lower elevations below 7300'. Above 7500' this rain crust is very strong, 4-6'' thick with 8-10'' of storm snow on top. Below this rain crust there is some less dense snow creating a slightly upside down snowpack. These conditions did not produce any failures with stability tests, CT's and ECT's, and also no results with large cornice drops. All the slab failures today were from a wind slab that developed last night into today with the increased winds. This heavier wind slab is now sitting on top of the lower density storm snow from Monday. Cornices are still very tender and easily failed with a ski kick. Crown lines were all under 1' deep and had limited propagation and limited downhill runs. SW winds were still wind loading slopes through today. Although the windward slopes were getting scoured down to the rain layer and had limited available snow left for transport. Photo 1,2,3: Small windslab failures with skier triggered cornice drops on slope. N-NE aspects, wind loaded terrain, 7300-7600'.
Snowpack photos: 
Snowpit videos (tests, etc): 

negrocanyon2010 12 21 007

Weather Observations
Blowing Snow: 
Yes
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: 

By 11am light snowfall started and SW winds increase in speed.