Small remotely triggered wind slab avalanches on Carpenter Ridge.

Location Name: 
Carpenter Ridge
Region: 
Independence Lake Area
Date and time of avalanche (best estimate if unknown): 
Sat, 01/02/2016 - 10:15
Location Map: 
United States
39° 24' 44.8056" N, 120° 18' 42.9984" 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
Avalanche Observations
Avalanche Type: 
Dry
Slab
Slope: 
39degrees
Trigger type: 
Skier
Crown Height: 
Less than 1 ft
Aspect: 
North
Weak Layer: 
Old Snow
Avalanche Width: 
50ft.
Terrain: 
Near Treeline
Elevation: 
8 620ft.
Bed Surface: 
Old Snow
Avalanche Length: 
100ft.
Number of similar avalanches: 
2
More detailed information about the avalanche: 

SSW winds created significant amounts of wind transport in this area today, exceeding forecast expectations. Old snow on the ground was being scoured from S-SW-W aspects onto NW-N-NE aspects in this area today. Plums of blowing snow were visible mainly above treeline on surrounding peaks. Near treeline wind transport and wind loading was occurring on Carpenter Ridge. Actual instability was observed in only some of the wind loaded areas. Two small wind slab avalanches (size D1) were intentionally remotely skier triggered today at the noted lat/long. Crown height ranged from 10 to 30 cm. Slabs only extended 3 to 6 m down slope from the ridgetop. Slab hardness was 1F to 1F+ on top of an old snow weak layer of F hard near surface facets. Some large stellar, plate, and surface hoar crystals were also noted on the bed surface. Propagation exceed typical pockets of wind slab and had some persistent weak layer characteristics, possibly due to the snow crystal type(s) observed on the bed surface. While there was not enough snow involved in these avalanches to bury a person, there was enough mass to push a person around if the triggering had been unintentional and someone had been caught.

Photo: 1st remotely triggered avalanche, intentionally triggered by the forecaster in the photo. Note the shooting crack leading away from his ski tip.

Photo 2: Shows the extent of the wind slab. At its thickest it is about 30cm and quickly gets smaller as the distance from the ridge increases. 

Video: 2nd remotely triggered avalanche, intentionally triggered on adjacent terrain to the 1st avalanche.

Avalanche Photos: 
Avalanche observation video: 

Small wind slab on a NNE facing test slope on Carpenter Ridge

Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
75% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Strong
Precipitation: 
None
Air temperature trend: 
Static
Wind Direction: 
Southwest