Forecaster Observation - Marion Lake, Flathead Range

Location Name: 
Forecaster Observation - Marion Lake, Flathead Range
Region: 
Flathead Range - Middle Fork Corridor
Date and time of avalanche (best estimate if unknown): 
Tue, 12/22/2015 - 12:30
Location Map: 

Red Flags: 
Recent avalanche activity
Recent loading by new snow, wind, or rain
Observation made by: Forecaster
Avalanche Observations
Avalanche Type: 
Dry
Slab
Slope: 
35degrees
Trigger type: 
Skier
Crown Height: 
1 ft
Aspect: 
Southeast
Weak Layer: 
Within storm snow
Avalanche Width: 
40ft.
Terrain: 
Below Treeline
Elevation: 
6 500ft.
Bed Surface: 
Old Snow
Avalanche Length: 
200ft.
More detailed information about the avalanche: 

Relatively small very soft slab avalanche was easily triggered from the top of a convex rollover that then ran downslope about 200 feet. The avalanche was fairly slow moving, but entrained enough snow to potenitally catch, carry, and even bury a person.

Other small natural soft slabs were also observed on slopes greater than 35 degrees. These slabs were about 30 feet wide and appeared to occur earlier in the storm overnight as the crowns were about 8-10 inches deep.

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

Snowfall accumulated in the morning at 0.5-1.0 inch per hour, then tapered. In the mid-afternoon southwest winds increased to moderate and began transporting snow. Visibilty was limited so we could not see into the alpine areas and upper ridgelines.

Activity: 
Skiing