Observations from Castle Peak

Location Name: 
Castle Peak
Region: 
Donner Summit Area
Date and time of observation: 
Mon, 11/21/2016 - 12:00
Location Map: 
United States
39° 22' 17.544" N, 120° 21' 10.9692" W
See map: Google Maps
US


Red Flags: 
Recent avalanche activity
Recent loading by new snow, wind, or rain
Observation made by: Forecaster
Snowpit Observations
More detailed information about the snowpack: 

New snow amounts of 50 to 60 cm (20 to 24 inches) were widespread and evenly distributed on all aspects in the Castle Peak area from 7,200' on up to the highpoint of travel at 8,800'. A few small isolated wind pillows existed along ridgetops, but no sizeable wind slabs extending down slope were observed. No signs of active slab avalanche instability were observed while on tour in the area.

Some very small soft slab avalanche debris (size D1) and the remains of a 20 cm (8 inch) crown that appeared to have occurred yesterday were observed on a NE aspect at 8,800' (photo 2). The avalanche appeared to have been no more than 10 m (33') wide and the slab had very limited down slope extent. The avalanche appeared to have occurred naturally, triggered by a very small cornice collapse. A witnessed very small natural cornice collapse today triggered a tiny amount of loose dry sluff adjacent to this slab avalanche from yesterday.

Contact with another party that had been traveling on steep NE aspects between Castle Peak and Basin Peak reported minor loose dry snow instability in steep rocky areas.

Forecaster party testpits at 39.371540, -120.353047 (NE aspect, 8,740') and 39.367480, -120.353895 (NW aspect, 8,760') showed that new snow was well bonded to the old snow surface of ice. No evidence existed of previously observed old snow above the basal ice layer. (This old snow was possibly assimilated to the ice layer by rain on Nov 16?)

Photo 1: New snow amounts of 50 to 60 cm (~2 feet) at Castle Pass, uniform coverage on all aspects at this elevation. Good supportability with ski penetration 10 to 15 cm (4 to 6 inches) in most areas, up to 30 cm (12 inches) in isolated areas.

Photo 2: Some of the soft slab debris from the size D1 avalanche noted above.

Snowpack photos: 
Weather Observations
Blowing Snow: 
No
Cloud Cover: 
100% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Light
Precipitation: 
Snow
Air temperature trend: 
Warming
Wind Direction: 
Southwest
Accumulation rate: 
Less than 1 in. per hour
More detailed information about the weather: 

Near continuous snowfall was observed in the Donner Pass/Castle Peak areas today while on location from 9 am to 2 pm. Additional accumulation was less than 5 cm (2 inches). Very limited sun through cloud cover occurred between periods of snowfall, just enough to occationaly cast a shadow.