Reactive Snow Pit below Castle Peak

Location Name: 
Castle Peak West Ridge
Region: 
Donner Summit Area
Date and time of observation: 
Sun, 12/13/2015 - 14:15
Location Map: 
United States
39° 21' 57.5136" N, 120° 21' 59.5188" W
See map: Google Maps
US


Red Flags: 
Whumphing noises, shooting cracks, or collapsing
Recent loading by new snow, wind, or rain
Observation made by: Public
Snowpit Observations
More detailed information about the snowpack: 

We dug a hasty pit that revealed significant instability on a leeward northern aspect after rapid loading from last night's storm.  Snow depth on this small, 39 degree test slope was 145cm (almost double the windward side).  While digging, loose chunks of snow fell out from several layers of the pit wall, indicating a poorly bonded, upside-down, complex snowpack.

An ECT failed during isolation of the back wall at 40cm deep from the snow surface above a small crust.  The failure propagated across with a Q1 shear quality (first photo).  Impressed by the reactive result, I reached about 30cm above the ECT to try a quick shovel shear test.  With hardly a pull, I triggered the whole test slope above me (second photo, with probe now moved to the top of the ECT).  Crunched for time, we didn't get to carefully study the failed layer or collect a full pit profile.  Needless to say we did not venture on any larger slopes of this kind.

The southern, windward aspects we quickly assessed elsewhere during the day seemed much more stable.

Snowpit or crown profile photo or graph: 
Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
100% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Moderate
Precipitation: 
Snow
Air temperature trend: 
Wind Direction: 
Accumulation rate: 
Greater than 1 in. per hour
More detailed information about the weather: