Instability on Castle Peak

Location Name: 
Castle Peak
Region: 
Donner Summit Area
Date and time of observation: 
Sat, 11/19/2011 - 11:37
Location Map: 
United States
39° 21' 56.736" N, 120° 21' 35.604" 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: Forecaster
Snowpit Observations
More detailed information about the snowpack: 

Above 8000 ft on the NW-N-NE-E aspects on Castle Peak the snow from earlier in the November persisted. This older snow has weakened and turned into sugary snow called facets. This layer is soft and has very little cohesion.

The storm over the last 24 hours exceeded expectations in this area and dropped 6-12 inches of new snow on top of these layers.

Several skier-triggered whumphs occurred on northerly slopes above 8000' due to failure of the older facetted snow.

Snowpit #1:

This pit is located at the coordinates listed in this observation. It was dug below treeline in an area protected from the wind. Stability tests in this pit showed instability due to the older facet layer not being able to support the new snow.

Snowpit #2

This pit was located near treeline about 700 vertical feet above and .25 miles away from the previous pit. In this area the strong southwest winds during the storm had affected the snow surface. In some areas it had scoured the snow back to older crusts and in others it had deposited wind slabs up to 2 ft in depth. This pit was in a wind loaded area.

Video 1: Extended Column Test in snowpit  #1

Video 2: Extended Column Test in snowpit  #2

Snowpit or crown profile photo or graph: 
Snowpit videos (tests, etc): 

Snowpit tests on Castle Peak below treeline

Snowpit tests on Castle Peak near treeline

Weather Observations
Blowing Snow: 
No
Cloud Cover: 
100% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Moderate
Precipitation: 
Air temperature trend: 
Static
Wind Direction: 
Southwest
Accumulation rate: 
More detailed information about the weather: