Glide Avalanche on Great Northern

Location Name: 
Forecaster Observation - Great Northern, Flathead Range
Region: 
Flathead Range - Middle Fork Corridor
Date and time of avalanche (best estimate if unknown): 
Thu, 05/11/2017 - 12:10
Location Map: 

Red Flags: 
Recent avalanche activity
Obvious avalanche path
Observation made by: Forecaster
Avalanche Observations
Avalanche Type: 
Slab
Trigger type: 
Natural
Crown Height: 
5 ft
Aspect: 
Southwest
Terrain: 
Above Treeline
Elevation: 
7 800ft.
Bed Surface: 
Ground
More detailed information about the avalanche: 

Observed a recent glide avalanche on the SW face of Great Northern that triggered a wet slab below it, both about 5 feet deep failing at or just above the ground.  I'd guess it ran mid-week.  Debris piles were extensive and at least 15 feet deep in places, with numerous flattened trees.  WS-N-R3-D3.5-G.

Avalanche Photos: 
Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
100% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Moderate (Small trees sway)
Precipitation: 
Snow
Air temperature trend: 
Static
Wind Direction: 
Southwest
Accumulation rate: 
Less than 1 in. per hour
More detailed information about the weather: 

About 1" of new snow at higher elevations, with some light snow transport from SW winds.  Overcast skies. 

Activity: 
Skiing