Professional Observation - WMR Avalanche Control West Bowl

Location Name: 
Professional Observation - WMR/West Bowl
Region: 
Whitefish Range - Southern (south of Coal Creek)
Date and time of avalanche (best estimate if unknown): 
Thu, 12/25/2014 - 10:00


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: Public
Avalanche Observations
Avalanche Type: 
Dry
Slab
Slope: 
35degrees
Trigger type: 
Other - explain below
Crown Height: 
2 ft
Aspect: 
South
Weak Layer: 
Other - explain below
Avalanche Width: 
225ft.
Terrain: 
Near Treeline
Elevation: 
6 200ft.
Bed Surface: 
Old Snow
Avalanche Length: 
600ft.
Number of people caught: 
1
More detailed information about the avalanche: 

On December 25th the WMR ski patrol conducted avalanche control in the West Bowl (Hellroaring Basin) area of the resort.  This area had not yet been open to the public for the 2014-15 season and control work was first initiated in this area two days prior.  Therefore this area had a snowpack similar to a backcountry snowpack as of Christmas Day.

Explosives and ski cutting produced very good results on aspects that ranged from NW-W-SW-S-SE.  Collapsing (whumpfing) occured on all of the above aspects during our routes.  Due to the sizable results and concerning audible failures explosives were used liberally (22 2-pound charges).  Most slides were soft slabs (4F+) that involved all of the surface snow sliding on the underlying crust.  Crown depths averaged 2 feet and most slides ran nearly full path. 

We assume that the weak layer was the buried surface hoar that is causing widespread avalanches throughout our region.   Ski cutting in one location released with a slab avalanche 2 feet in depth, 50' wide and ran 600' vertical to the valley floor.  

Due to the complexity of the avalanche problem we did not open West Bowl until approximately noon.  

Avalanche Photos: 
Weather Observations
Cloud Cover: 
Clear
Air temperature: 
Below Freezing
Air temperature trend: 
Warming
Activity: 
Skiing