Whumpfing on N aspects at 9200 feet below tree line

Location Name: 
Sonora Peak, Silver Creek Drainage
Region: 
Outside of the Forecast Area
Date and time of observation: 
Thu, 03/22/2012 - 15:15
Location Map: 
United States
38° 22' 23.8404" N, 119° 34' 43.0644" W
See map: Google Maps
US


Red Flags: 
Whumphing noises, shooting cracks, or collapsing
Observation made by: Public
Snowpit Observations
More detailed information about the snowpack: 

Traveled from snow line at approx 8000 feet to 9200 feet test roll over on N aspect. Probed along the way to identify persistent weak layer on NW-N-NE aspects. Felt consistent weak layer under harder crusts about 50 cm down. Located test plot on N aspect at 20 degrees. 100cm HS. Faceted layer located 40-50 cm down. CTV 50cm down on faceted layer with percolation tubes. ECTP 15, 50cm down with percolation tubes. Signs of free water observed down into the persistent faceted layer of concern. 40cm of P/1F over weak layer supporting further wet slab concern.

The snow pack appears to be shallower the further south in the Sierras. The probability of triggering and propogating the weak faceted layer may be more likely as the persistent layer is within the 20-85cm sweat spot.

Weather Observations
Blowing Snow: 
No
Cloud Cover: 
100% of the sky covered by clouds
Air temperature: 
Wind Speed: 
Light
Precipitation: 
None
Air temperature trend: 
Wind Direction: 
West
Accumulation rate: 
More detailed information about the weather: 

Poor freezing of the surface at 9200 with minimal melt freeze curst observed. Warm temperatures and 50-100% cloud cover has kept temps warmer than usual. Signs of free water observed in the top 50 cm of the snowpack.