Shooting cracks, test slope failure, and lots of wind transport on Hidden Peak

Location Name: 
Hidden Peak
Region: 
West Shore Area
Date and time of observation: 
Thu, 03/24/2011 - 13:30
Location Map: 
United States
38° 59' 1.6152" N, 120° 7' 46.4268" 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: Forecaster
Snowpit Observations
More detailed information about the snowpack: 

By 2pm widespread skier-triggered shooting cracks and test slope failures occurred at all elevations above 7000 ft in this area. Strong winds below treeline had created fragile wind slabs on any open terrain and even on some more sheltered terrain. Ski cuts on these slabs would cause the slopes to shatter and produce failures 1-2 ft in depth with the deeper slabs being in the more wind-loaded higher elevation terrain. In below treeline terrain these slabs measured 10-20 ft wide and would move downhill for 20-30 ft. At 8200 ft 2 natural avalanches had occurred around midday on E-NE aspects, 38-40 degrees in steepness with 18 inch crowns. These slides ran down hill for aprox. 400-500 ft. Above treeline skier triggered cracking became even more widespread. Wind speeds increased to 90-100 mph with gusts over 120 mph. These winds transported so much snow that visibility was reduced to 10-20 ft above treeline. I was not able to see whether or not the avalanche paths near the top of Hidden had released or not.

Photo 1: Cracking below treeline

Photo 2: Cracking above treeline

Video 1:Wind transport below treeline

Video 2: Wind transport above treeline

Snowpack photos: 
Snowpit videos (tests, etc): 

201103324Hidden 001

201103324Hidden 007

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: 
Static
Wind Direction: 
Southwest
Accumulation rate: 
Greater than 1 in. per hour
More detailed information about the weather: 

Snowfall and winds started to increase dramatically around 11am. Snowfall rates reached 1.5-2 inches per hour through 2:30 pm. They showed no signs of decreasing at that point. Winds increased with strong steady winds below treeline and steady gale force winds above treeline. Gusts below treeline likely hit 60-80 mph while above treeline they reached into the 120 mph range. The winds were transporting significant amounts of snow at all elevations.