Widespread, shallow instabilities on Red Lake Peak

Location Name: 
Red Lake Peak
Region: 
Carson Pass Area
Date and time of observation: 
Fri, 12/14/2012 - 00:00
Location Map: 
United States
38° 42' 57.3156" N, 119° 58' 53.4648" 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
Obvious avalanche path
Observation made by: Professional Observer
Snowpit Observations
More detailed information about the snowpack: 

Widespread, human triggered, shallow soft slab avalanching today on Red Lake Peak. No observed avalanches were large enough to harm a person. Crowns were 15-40cm deep, up to 30m wide, and debris ran up to 250m. However, slab thickness was significantly shallower just down slope of start zones, minimizing harmful potential. Weak layer was storm snow density change 5-10cm above rain crust. Complex terrain with several wind loaded mid-slope features resulted in human triggered avalanching throughout Crater Lake drainage (several other people in the area today).

pic 1: Shallow human triggered crown.

pic 2: Triggered by 40lb dog.

video 1: 2x moderate ECTP on density change just above rain crust. Wind loaded, 40 degree slope, E aspect at 9000ft along approach from Meiss SnoPark. As elsewhere, slab thickness significantly reduced just 10m downslope. Clarification on rain crust comment: I did not mean to imply that rain crusts merged together over time, rather, at this location they formed as 1 thick crust with no facets in between.

video 2: Another moderate ECTP on density change just above rain crust. Wind loaded, 30 degree slope, N,NE aspect at provided lat/long. Poor audio - I was describing 1f hard wind slab on top of 4f hard storm snow.

video 3: PST 40/100 (end) on Dec 2nd facets, at same location as video 2. Not a concern at this location today as slabs did not remain thick beyond localized start zones. Note the planar failure on storm snow density change as I removed the column after test.

 

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

Very thin coverage of low density snow on E aspect exit from 7600ft to hwy 88

Weather Observations
Blowing Snow: 
Yes
Air temperature: 
Below Freezing
Wind Speed: 
Moderate
Precipitation: 
Snow
Air temperature trend: 
Static
Wind Direction: 
Southwest
Accumulation rate: 
Less than 1 in. per hour
More detailed information about the weather: 

Cloud cover and precip increased mid-day.