Professional Observation - John F.Stevens Canyon

Location Name: 
Professional Observation - John F.Stevens Canyon
Region: 
Flathead Range/Glacier National Park - John F. Stevens Canyon
Date and time of avalanche (best estimate if unknown): 
Tue, 12/20/2016 - 14:30


Red Flags: 
Whumphing noises, shooting cracks, or collapsing
Recent loading by new snow, wind, or rain
Observation made by: Professional Observer
Avalanche Observations
Avalanche Type: 
Dry
Trigger type: 
Skier
Crown Height: 
1 ft
Aspect: 
Southeast
Weak Layer: 
Within storm snow
Avalanche Width: 
150ft.
Terrain: 
Above Treeline
Bed Surface: 
Old Snow
Number of people caught: 
0
Number of partial burials: 
0
Number of full burials: 
0
More detailed information about the avalanche: 
  • On descent from the Shed 7 West ridge we triggered two small soft slab avalanches from safe terrain on the ridge that separates the Shed 7 East starting zone and the Shed 5 starting zone.  Both of these avalanches were triggered on southeasterly aspects and were soft slabs formed by recent windloading.
  • The largest of these two skier triggered avalanches had a crown that appeared to be greater than 50 meters (150’) in length and a crown depth that varied from 15 cm to 30 cm (0.5’ to 1’) in depth
  • Very difficult to view the results of these avalanches due to blowing snow.  Also, no photos taken due to reduced visibility
  • One relatively small soft slab natural avalanche was also observed on an east facing aspect at approximately 5500 feet elevation in the starting zone of Shed 5 or what we refer to as “Test Slope 3.”  Debris associated with this avalanche terminated in the starting zone.
  • Other signs of obvious instability were also noted on descent which included shooting cracks and snowpack collapsing 

BNSF AVALANCHE SAFETY FIELD OBSERVATIONS SUBMITTED TO FLATHEAD AVALANCHE CENTER AND GLACIER NATIONAL PARK ARE BEING PROVIDEDED IN ACCORDANCE WITH THE TERMS AND CONDITIONS SPECIFIED GLACIER NATIONAL PARK SPECIAL USE PERMIT.  

THESE OBSERVATIONS REPRESENT SITE SPECIFIC INFORMATION INTENDED FOR THE BNSF AVALANCHE SAFETY PROGRAM AND IN NO WAY ARE TO BE CONSTRUED AS A PUBLIC/ RECREATION AVALANCHE FORECAST.  

Weather Observations
Blowing Snow: 
Yes
Air temperature: 
Below Freezing
Wind Speed: 
Moderate (Small trees sway)
Precipitation: 
Snow
Air temperature trend: 
Warming
Wind Direction: 
Southwest
Accumulation rate: 
Less than 1 in. per hour
More detailed information about the weather: 

Overcast skies, moderate south-southwest winds with strong gusts, and air temperatures in the upper 20s F at all elevations.  Intermittent snowfall throughout the day with light snowfall accumulations.

Activity: 
Skiing