Unstable wind slabs on Castle Peak.

Location Name: 
Castle Peak
Region: 
Donner Summit Area
Date and time of observation: 
Mon, 01/02/2017 - 10:45
Location Map: 
United States
39° 21' 52.578" N, 120° 21' 33.8724" 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: Forecaster
Snowpit Observations
More detailed information about the snowpack: 

New snow amounts in this area were 55 to 60 cm (~2 feet) of low density snow as of 9:30 am this morning. Snowfall continued all day generally at S2, occasionally at S1. Upon reaching treeline at Castle Pass, unstable wind slabs were prevalent. Some small natural wind slab avalanches had occurred along the ridge triggered by natural cornice collapse. Otherwise every test slope that we approached that was steeper than 35 degrees easily avalanched. Snowpack failure was observed to occur within the top 30 cm (1 foot) of new snow. Slabs were typically F+ to 4F- on top of a F hard storm snow weak layer. Total wind loaded amounts in these same areas was typically 90 to 120 cm (3 to 4 feet).

Higher up of the NW side of Castle Peak, a test pit revealed very easy propagating results at the old/new snow interface.

Snowpit or crown profile photo or graph: 
Snowpack photos: 
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: 
Static
Wind Direction: 
Southwest
Accumulation rate: 
Greater than 1 in. per hour