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Unstable cornices and wind slab avalanche

Location Name: 
Eddy Range - Parks Creek summit area
Region: 
Mt Eddy
Date and time of avalanche (best estimate if unknown): 
Tue, 02/21/2017 - 7:00pm
Observation made by: 
Forecaster
Red Flags: 
Recent avalanche activityWhumphing noises, shooting cracks, or collapsing

Location Map

United States
41° 20' 42.0936" N, 122° 30' 44.6508" W
US

Avalanche Observations

Details

Two easily triggered cornices features in areas of little consequence were observed yesterday, 2/20. Also, a natural wind slab avalanche was observed on a northerly facing slope above treeline. A full investigation was not conducted. This avalanche was viewed from afar. 

Photos

Characteristics

Avalanche Type: 
Slab
Trigger type: 
Natural
Slope: 
37degrees
Aspect: 
North
Elevation: 
7 800ft.
Terrain: 
Above Treeline
Weak Layer: 
Unknown
Bed Surface: 
Unknown
Crown Height: 
1 ft
Avalanche Width: 
150ft.
Avalanche Length: 
900ft.
Number of people caught: 
0
Number of partial burials: 
0
Number of full burials: 
0

Weather Observations

Details

A very alpine feel was present up in the Eddies yesterday with sunlight filtering through thin clouds and more dense clouds passing by blocking the sun from time to time. Periods of very light snow and graupel fell. No accumulation. The snow below 6,800 feet began to become heavy and even formed a slight temperature crust later in the day. This will likely be a zipper crust now. Above 7,000 feet, snow surfaces were smooth and soft. From 6,500 to 7,000 feet, this elevation band is transitional. Winds were not noticeable below treeline. Near treeline a few gusts came through but otherwise was nice. Above treeline, moderate winds blew out of the south. Temperatures were below freezing all day.

Statistics

Cloud Cover: 
75% of the sky covered by clouds
Blowing Snow: 
Yes
Precipitation: 
Snow
Accumulation rate: 
Less than 1 in. per hour
Air temperature: 
Below Freezing
Air temperature trend: 
Cooling
Wind Speed: 
Light
Wind Direction: 
South