Test slope failures near Lincoln Ridge

Location Name: 
Lincoln Ridge
Region: 
Yuba Pass Area
Date and time of avalanche (best estimate if unknown): 
Wed, 03/23/2011 - 13:15
Location Map: 
United States
39° 36' 33.0084" N, 120° 29' 22.7976" 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
Avalanche Observations
Avalanche Type: 
dry,slab,
Slope: 
40degrees
Trigger type: 
Skier
Crown Height: 
1 ft
Aspect: 
North
Weak Layer: 
Storm Snow
Avalanche Width: 
20ft.
Terrain: 
Near Treeline
Elevation: 
7 200ft.
Bed Surface: 
Storm Snow
Avalanche Length: 
40ft.
Number of similar avalanches: 
5
More detailed information about the avalanche: 

4-6 inches of new snow had accumulated by 2 pm in this area. In below treeline, non-wind-loaded areas ski cuts on steep test slopes would produce loose sluffs that entrained the top 3-4 inches of the new snow. Ski cuts and ski kicks on near and below treeline, open, wind-affected and wind-loaded test slopes steeper than 37 degrees produced small soft slab avalanches. These slabs measured about 1 ft. in depth. They entrained all of the new snow and failed on a density change about 2 inches below yesterdays snow surface.

Near and above treeline visibility was limited due to fog and blowing snow. No signs of natural activity were observed on some of the steep wind-loaded slopes in the area. Some skier-triggered shooting cracks did occur on wind loaded slopes.  Ski cuts on a 39 degree, wind-loaded test slope at 7600 ft produced results similar to those on the near and below treeline test slopes but with a slightly thicker wind slab 18 in.

Photo 1 and Video: Soft slab on a wind-loaded test slope below treeline. Marked on the map.

Photo 2: Sluffing on a steep non-wind-loaded slope below treeline.

Photo 3: Shooting cracks in a wind slab above treeline at 7600 ft. on Lincoln Ridge. (South of the marker on the map)

Avalanche Photos: 
Avalanche observation video: 

201103323Lincoln 002

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
More detailed information about the weather: 

Snowfall of .75-1 in per hour with southwest winds during the day in this area. 4-6 inches of new snow by 2pm.