Avalanche on Snowshed Mtn

Location Name: 
BNSF Avalanche Safety - Snowslip Mtn. GNP
Observation date: 
Wednesday, December 23, 2020 - 22:45
Is this an Avalanche Observation: 
Yes
Observation made by: Public

Location

Tabs

Quick Observation
  • Toured up the ridge above Burnout and the Shed 4D/5 avalanche paths and then farther on into the upper starting zone of Shed 7 West to a highpoint at ~6600’. Then made road observations and checked manual weather stations on the Canyon floor.
  • Descended the Shed 5 Path.
  • Objectives were to look for any recent avalanche activity, determine the upper elevation limit of the Dec 22nd crust, assess the past 48-hour snowfall totals and recent wind-loading, and obtain a full snow pit profile in the Shed 7 area.
  • No avalanche activity observed in the Program Area, but noticed an avalanche crown from Hwy 2 on the SE face of Snowshed Mountain above Sheep Creek (photo) in the Flathead Range. This appeared to be at least D2 in size and likely failed on a more deeply buried persistent week layer. Estimating that it ran sometime during the Dec 21-22 overnight warm-up.
  • About 4-5” snow from yesterday on top of the Dec 22nd crust at the Canyon floor. The snowpack below the crust was moist at low-mid elevations.
  • Around 6500’ the Dec 22nd crust eventually disappeared and there was about 6-10” of new snow from yesterday and the snowpack became dry throughout.
  • Recent wind-loading was minimal with very little new wind slab development at all elevations we travelled through.
  • Snow profile conducted in the Shed 7 West Path at 6600’ on a southeast aspect. Dec 9th crust/facet combo was about 28” below the surface here. No propagation with an Extended Column Test (pit profile with more details in photo).
  • No shooting cracks, audible collapses, or any other signs of instability during the ski tour.
  • Mostly overcast skies with occasional breaks that allowed for some brief sunshine. Clearing skies by late afternoon/sundown.
  • Very light snow coming down as on again/off again showers with trace accumulations over the day.
  • Light and variable winds at all elevations.
  • Daytime high air temperatures reached the mid-20s °F on the Canyon Floor and the mid-teens °F at elevations above 6000’.
Snowpack, Avalanche, Weather Images: 
Travel Details
Region: 
Flathead Range/Glacier National Park - John F. Stevens Canyon
Activity: 
Skiing
Avalanche Details
Avalanche Details: 
Date and Time of Avalanche: 
Tuesday, December 22, 2020 - 02:00
Number of avalanches: 
1
Avalanche Type: 
Hard Slab
Failure Plane/Weak Layer: 
Old snow
More information or comments about the avalanche: 

Observed from HWY 2 and all details are rough estimates.

Hide Trigger
Trigger: 
natural
Hide Terrain
Aspect: 
Southeast
Starting Elevation: 
above-treeline
Hide Size
Destructive Size: 
D2.5
Relative Size: 
R2 Small
Crown Height: 
3 ft
Avalanche Width (Average width): 
300ft.
Avalanche Location: