Sensitive wind slabs on Wildflower Ridge

Location Name: 
Wildflower Ridge
Region: 
Donner Summit Area
Date and time of observation: 
Fri, 12/19/2014 - 12:30
Location Map: 
United States
39° 18' 25.488" N, 120° 19' 5.088" 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: 

Sensitive wind slabs had formed on Wildflower Ridge (NE aspect, 7,800') by mid day. At 12:30pm, test slope failures were prevalent on slopes steeper than 40 degrees with wind slabs failing 10 to 25 cm deep (4 to 10 inches). Slabs were 4F to 1F hard, failing on a weak layer of F hard storm snow. Gale force winds and blowing snow made exact crystal identification of weak layer impossible. Skier triggered fractures were observed to propagate up to 40'.

New snow amounts had reached the upper end of forecast amounts at 12:45pm with 5 inches of new snow noted in wind protected areas at 8,000'.

Photo 1: Skier triggered wind slab on test slope. Propagation of 40' from trigger point.

Photos 2&3: Smaller skier triggered wind slab on test slope ~20cm deep.

Photo 4: Skin track refilling after 1 hr in a mostly wind protected area.

Snowpack photos: 
Snowpit videos (tests, etc): 

20141219 Small wind slabs on Wildflower Ridge, Mt. Judah, CA

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

Snow accumulation rates just shy of 1 inch per hour were observed from arrival on Donner Pass at 10:15am until 12:30pm. Around 12:30pm, wind speed abruptly dropped from gale force to moderate speed, visibility improved, and snow accumulation rate decreased.