Cornices and Sluffing in Negro Canyon

Location Name: 
Negro Canyon
Region: 
Donner Summit Area
Date and time of observation: 
Fri, 02/24/2017 - 13:30
Location Map: 
United States
39° 20' 47.562" N, 120° 18' 21.4488" W
See map: Google Maps
US


Red Flags: 
Observation made by: Forecaster
Snowpit Observations
More detailed information about the snowpack: 

A "right side up" snowpack exists in this area with soft unconsolidated snow on the surface and progressively more dense storm snow below. At the base of the recent snow there is a frozen rain crust. Soft surface snow existed on W-NW-N-NE-E aspects into the afternoon with a variable breakable sun crust on the SE-S-SW aspects. Large cornices existed above wind-loaded slopes. Ski kicks well away from the edges of these cornices would cause them to break above small wind-loaded test slopes but the large cornice pieces impacting the slope below did not trigger any cracking or signs of wind slab instability.  Ski cuts on steep NE-N facing slopes did trigger loose dry sluffs that involved the topmost 4-5 inches of unconsolidated surface snow.

Photo 1: Ski cut triggered loose dry sluff on a N aspect at ~7500 ft.

Photo 2: Cornice failure caused by ski kicks on a ENE aspect at 7200 ft.

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