Reactive Wind Slabs, Storm Slabs, and Shooting Cracks on Hidden Peak

Location Name: 
Hidden Peak
Region: 
West Shore Area
Date and time of observation: 
Sun, 12/23/2012 - 11:30
Location Map: 
United States
38° 58' 49.98" N, 120° 7' 5.736" 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: Professional Observer
Snowpit Observations
More detailed information about the snowpack: 

A mix of wind slabs and storm slabs up to 40cm deep were present in below treeline terrain. These slabs were failing easily with ski cuts on small convex terrain features.  Many shooting cracks and cracking around skis were also present in these areas.  Our snowpit (on a NE aspect, 8200', 35 degree slope) revealed around 120cm of snow on top of the 12/2 rain crust.  The 12/12 facet layer on top of the rain crust is present here and is 10cm thick.  The 12/2 facet layer below the rain crust is present but irregular and was not consistent across the snow pit.  We had very easy results with ECT's on the windslab and was consistently failing during isolation of the column.   

Photo #1:  Small convex rollover with a ski cut had windslab failure with shooting cracks out to lower angle terrain.  7700', east aspect, 35 degree slope, below treeline.

Photo #2: A fractured slope in below treeline terrain. This storm slab failed as a result of ski cut on the convex roll.

Video: ECT from the snowpit.

 

Snowpack photos: 
Snowpit videos (tests, etc): 

2012 12 23 Hidden 001

Any other comments about the observation or links to outside pages that have more info on the observation: 

Below 7500 ft. coverage remains a little spotty. Rocks and trees are still barely covered below this elevation.

Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
100% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Strong
Precipitation: 
Snow
Air temperature trend: 
Static
Wind Direction: 
Southwest
Accumulation rate: 
Greater than 1 in. per hour
More detailed information about the weather: 

A small break in the storm mid morning.  By mid day snow was heavy above 1'' per hour.  Consistent strong SW winds throughout the day.