Path 1183 Avalanche

Location Name: BNSF Avalanche Safety - Flathead Range Observation date: Monday, March 7, 2022 - 22:45	Is this an Avalanche Observation: Yes

Observation made by: Public

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Quick Observation

Ascended to the upper starting zone of Path 1183, an avalanche path named for its proximity to the railway milepost.
Objectives were to investigate the avalanche that ran within 100 yards of the rail grade last week in this path, look for other nearby avalanche activity nearby, and to assess the current snowpack conditions

No recent avalanche activity observed, but we saw multiple storm slab crowns and wet loose avalanches from last week’s impressive and widespread avalanche cycle. Details under the Avalanche Tab.
The avalanche in Path 1183 likely ran sometime in the early morning hours of March 1st
Other notable avalanche activity included multiple crowns in the Cascadilla and Wahoo basins. All of these appeared to be storm slabs and up to D2 in size.
On the SE face of Triangle Ridge above Great Bear Creek, we noticed two large crowns, one running for several hundred feet (size D2.5 at least).

Rock hard surface crust everywhere, 4-6+” thick, that is supportable in skis and often even in boots. On the Canyon floor there is a trace of recent snow on top of the crust and at our high point at 5900’ there’s about 5”. This snow fell late last week and has mostly turned into weak facets.
No wind-loading observed on our route and we did not see any blowing/drifting snow up high on Nyack Mtn above us.
Currently no signs of instability observed.
Broken skies and occasional sunshine with no precipitation and calm winds all day.
Air temperatures reached the mid-30s °F on the Canyon floor and the mid-20s °F at 6000’ by late afternoon

Snowpack, Avalanche, Weather Images:

Travel Details

Region:

Flathead Range - Middle Fork Corridor

Activity:

Skiing

Avalanche Details

Avalanche Details:

Date and Time of Avalanche:

Tuesday, March 1, 2022 - 05:45

Number of avalanches:

Avalanche Type:

Soft Slab

Failure Plane/Weak Layer:

New/old snow interface

More information or comments about the avalanche:

It initiated as a storm slab at the top of the path at 5700’ elevation, on a NE aspect, failing on the storm slab interface. The crown today was 1-2 feet thick and about 700’ wide (photo). Associated debris entrained a fair amount of wet debris on the way to the valley floor.
Additional wet loose avalanches ran afterwards and may have contributed to the debris pile in the runout.
This was a destructive size 2.5 with debris running 2200’ vertical feet, flowing over old US Hwy 2 and under the FEC powerlines. The debris pile was about 25’ deep at the deepest and 40-70’ wide with some small broken trees in it (photo).

Trigger

Trigger:

natural

Terrain

Start Zone Slope Angle:

Aspect:

Northeast

Starting Elevation:

5700

Size

Destructive Size:

D2.5

Relative Size:

R3 Medium

Crown Height:

2 ft

Avalanche Length (Vertical Run):

2200ft.

Avalanche Width (Average width):

700ft.

Avalanche Location:

Date and Time of Avalanche:

Tuesday, March 1, 2022 - 05:45

Number of avalanches:

Avalanche Type:

Soft Slab

Failure Plane/Weak Layer:

New/old snow interface

More information or comments about the avalanche:

Observed at least a couple more D2 storm slabs in the Wahoo basin. Also multiple wet loose up to D2.

Trigger

Trigger:

natural

Terrain

Aspect:

Northeast

Starting Elevation:

near-treeline

Size

Destructive Size:

D2 Could bury, injure, or kill a person.

Relative Size:

R2 Small

Crown Height:

2 ft

Avalanche Location:

Date and Time of Avalanche:

Monday, March 1, 2021 - 05:45

Number of avalanches:

Avalanche Type:

Soft Slab

Failure Plane/Weak Layer:

New/old snow interface

More information or comments about the avalanche:

At least two impressive crowns on Triangel Ridge above Great Bear Ck. One looked like it had run 800 to 1000 feet or more. Could not see the debris and other details about these avalanches unknown.

Trigger

Trigger:

natural

Terrain

Aspect:

East

Starting Elevation:

near-treeline

Size

Destructive Size:

D2.5

Relative Size:

R3 Medium

Crown Height:

2 ft

Avalanche Location:

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