New wind slabs and new snow on Lincoln Ridge

Location Name: 
Lincoln Ridge
Region: 
Yuba Pass Area
Date and time of observation: 
Tue, 02/19/2013 - 12:30
Location Map: 
United States
39° 35' 24.0504" N, 120° 29' 21.4512" W
See map: Google Maps
US


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

2-3 inches of snow fell overnight in the Lincoln Ridge area. Snowfall intensity increased today and an additional 3-4 inches accumulated by 1pm. On the northerly aspects, this new snow rested on top of a mix of old near surface facets, thin breakable melt freeze crusts, and older supportable rain crusts. The new snow had not overloaded these older snow surfaces by 1pm today. Within the new snow a change in density between the snow that fell last night and the snow that continues to fall today was reactive to tests and ski cuts. Multiple skier triggered shooting cracks and some small test slope failures occurred due to a failure at this density change. Only 3-4 inches of snow existed above this weak interface in most areas. On one heavily wind loaded test slope, the soft slab above this density change measured about 8 inches deep.

Photo 1: Snowpack stratigraphy on a wind loaded NE facing test slope at 7760 ft. This photos shows the various interfaces and weak layers in the upper portion of the snowpack.

Photo 2: Skier triggered cracks on a NE facing wind loaded test slope at about 7800 ft.

Photo 3: Skier triggered test slope failure on a NNE facing, 39-42 degree wind loaded test slope at about 7760 ft.

Photo 4: The other side of the test slope pictured in photo 3. At the point where the most wind loading had occurred the soft slab had reached about 8 inches in depth.

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: 
Strong
Precipitation: 
Snow
Air temperature trend: 
Cooling
Wind Direction: 
Southwest
Accumulation rate: 
Greater than 1 in. per hour
More detailed information about the weather: 

Snowfall rates measured at 1in per hour.