Cornices and Surface Hoar in Negro Canyon

Location Name: 
Negro Canyon
Region: 
Donner Summit Area
Date and time of observation: 
Tue, 02/28/2017 - 09:00
Location Map: 
United States
39° 21' 3.69" N, 120° 18' 11.0952" W
See map: Google Maps
US


Red Flags: 
Recent loading by new snow, wind, or rain
Rapid warming
Observation made by: Forecaster
Snowpit Observations
More detailed information about the snowpack: 

Soft unconsolidated snow existed on top of more dense consolidated snow on the NW-N-NE aspects near Negro Canyon. This "right-side-up" snowpack did not produce signs of instability in sheltered areas. Snowpit tests and hand pits indicated good bonding between the new and old snow and within the snow layers (2 ECTN's and 1 ECTX in the top 1m of the snowpack at various locations between 6800 and 7600 ft on NW-N-NE aspects). Some surface hoar up to 3-4 mm had formed on these aspects as well. Near the ridgelines, large cornices existed and ski kicks well away from the edges triggered failures in the cornices. The large cornice pieces that dropped onto the wind-loaded slopes below did not produce any cracking or wind slab failures.  

On W and E aspects, dust on breakable crust conditions existed and on the more southerly aspects, the crust became more supportable. 

Snowpack photos: 
Weather Observations
Blowing Snow: 
No
Cloud Cover: 
25% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Calm
Precipitation: 
Air temperature trend: 
Warming
Wind Direction: 
Accumulation rate: 
More detailed information about the weather: 

Clearing skies and warming temperatures during the tour.