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Snowmobile triggered wind slab in the Old Ski Bowl

Location Name: 
Old Ski Bowl
Region: 
Mt. Shasta
Date and time of avalanche (best estimate if unknown): 
Sat, 01/27/2018 - 11:00am
Observation made by: 
Forecaster
Red Flags: 
Recent avalanche activityWhumphing noises, shooting cracks, or collapsingRecent loading by new snow, wind, or rainRapid warming

Location Map

96067 Mount Shasta , CA
United States
41° 22' 4.3968" N, 122° 11' 47.4252" W
California US

Avalanche Observations

Details

SS-AM-R4-D1-S (soft slab, artificially triggered by a snowmobile, large relative to the avalanche path, relatively harmless destructive force, bed surface within new snow)

A snowmobile triggered wind slab avalanche occurred today on an east-facing slope above treeline at 8,400ft in the Old Ski Bowl. The avalanche broke 1-3ft deep, 250ft wide, and ran 10-20ft downslope. The avalanche failed on a density break within new snow. No one was caught, buried or injured.  Westerly winds were actively loading leeward slopes and terrain features near and above treeline. Although this was a relatively harmless avalanche, the propagation was very impressive. 

Characteristics

Avalanche Type: 
Dry
Trigger type: 
Snowmobiler
Slope: 
35degrees
Aspect: 
East
Elevation: 
8 400ft.
Terrain: 
Above Treeline
Weak Layer: 
Storm Snow
Bed Surface: 
Storm Snow
Crown Height: 
3 ft
Avalanche Width: 
250ft.
Avalanche Length: 
20ft.
Number of similar avalanches: 
1
Number of people caught: 
0
Number of partial burials: 
0
Number of full burials: 
0

Weather Observations

Details

Strong westerly winds were steady throughout the day. In the afternoon, a brief rain event occurred up to 8,000ft. Skies were mostly obscured with short periods of sunshine.  

Statistics

Cloud Cover: 
75% of the sky covered by clouds
Blowing Snow: 
Yes
Precipitation: 
Rain
Accumulation rate: 
None
Air temperature: 
Above Freezing
Air temperature trend: 
Warming
Wind Speed: 
Strong
Wind Direction: 
West