Just one audible collapse?

Location Name: 
BNSF Avalanche Safety - Snowslip Mtn GNP
Observation date: 
Thursday, March 17, 2022 - 18:45
Is this an Avalanche Observation: 
Yes
Observation made by: Public

Tabs

Quick Observation
  • Ascended the ridge above the Burnout, Shed 4D, Shed 5, and Shed 7 avalanche paths. Descended the same route.
  • Objectives were to look for recent avalanche activity, assess the snowpack structure and stability in this area, and perform a welfare check on the Shed 4 and Shed 7 weather stations.
  • Recent avalanche activity included:
    • Multiple wet loose avalanches up destructive-size 1.5 (D1.5) ran this afternoon in Path 1163. Debris ran ½ path terminating well above the rail.
    • A D1.5-sized slab failed on an easterly slope just below a ridgeline at 6800’ in the Shields Ck basin, outside of the Program Area. Likely a wind slab, about a foot thick and 100’ wide.
    • A larger, at least D2-size slab on an easterly aspect at about 7200’ above Devil Creek. This may have run yesterday or the day before and may have failed on the facets associated with the early March crust (photo).
  • During the March 1st avalanche cycle a cornice fall triggered a small-medium sized slab in Shed 7 West. Remnants of the crown were still visible today. Associated debris was D2 size and terminated well above the grade.
  • Snowfall totals for March 15th/16th ranged from 2-4” on the Canyon floor to 7-12” above 6000’.
  • Below about 5500’ the snowpack was mostly wet throughout. Above this elevation the surface was wet on the surface on sunny aspects.
  • Above 6000’ the facets resting atop the early March crust were buried 1-3’ deep.
  • We experience one audible collapse at 6100’ on a north aspect. We expected additional collapses further up the ridge on similar aspects, but none occurred.
  • Minimal wind loading from the mostly light SW winds above 6000’.
  • Dug a hasty pit in the Shed 7 W avalanche path at 6700’ on an easterly aspect. Snow depth was 104”. ECTN14 and CT14 Q2 on the most recent storm interface about 12” down. The early March facets/crust were buried 20” down produced no fractures.
  • Dug a second hasty pit on a northerly slope in the Shields Ck. basin at 6700’. Here the early March facets/crust were buried about 32” deep and produced no fractures during stability tests.
  • Broken skies in the AM gave way to mostly clear conditions by the afternoon. No precipitation all day.
  • Calm winds on the Canyon floor and light SW winds at upper elevations with moderate gusts.
  • Air temperatures reached the mid-40s °F on the Canyon floor and the low-30s °F above 6000’ by the afternoon.
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: 
Thursday, March 17, 2022 - 08:00
Number of avalanches: 
1
Avalanche Type: 
Soft Slab
Failure Plane/Weak Layer: 
New/old snow interface
Hide Trigger
Trigger: 
natural
Hide Terrain
Aspect: 
East
Starting Elevation: 
above-treeline
Hide Size
Destructive Size: 
D1.5
Relative Size: 
R1 Very Small
Crown Height: 
1 ft
Avalanche Length (Vertical Run): 
300ft.
Avalanche Width (Average width): 
100ft.
Avalanche Location: 
Date and Time of Avalanche: 
Thursday, March 17, 2022 - 14:00
Number of avalanches: 
6
Avalanche Type: 
Wet Loose
Failure Plane/Weak Layer: 
Within storm snow
Hide Terrain
Start Zone Slope Angle: 
40
Aspect: 
South
Starting Elevation: 
near-treeline
Hide Size
Destructive Size: 
D1.5
Relative Size: 
R1 Very Small
Avalanche Location: 
Date and Time of Avalanche: 
Tuesday, March 15, 2022 - 22:00
Number of avalanches: 
1
Avalanche Type: 
Soft Slab
Failure Plane/Weak Layer: 
Old snow
More information or comments about the avalanche: 
  • May have been cornice fall triggered.
  • Crown height estimated and could size up crown width from the angle we were viewing.
  • Could not see runout.
  • Maybe failed on the early March facets?
Hide Trigger
Trigger: 
natural
Trigger Modifier: 
Cornice Fall Triggered
Hide Terrain
Start Zone Slope Angle: 
40
Aspect: 
East
Starting Elevation: 
above-treeline
Hide Size
Destructive Size: 
D2 Could bury, injure, or kill a person.
Relative Size: 
R3 Medium
Crown Height: 
2 ft
Avalanche Location: