DEEP in the Swan

Location Name: Forecaster Observation - Peter's Ridge, Swan Range Observation date: Tuesday, February 12, 2019 - 19:30	Is this an Avalanche Observation: Yes

Observation made by: Forecaster

Location

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Quick Observation

We traveled on the west side of the Swan Crest to observe the effects of the recent storm snow at mid-elevations.

In wind sheltered terrain the surface snow was comprised of 18-24" of low-density snow. The top 3-4" was soft (F-) but cohesive enough to allow for cracking and a shallow storm slab cycle early this morning.
In wind affected terrain, slab formation up to 1' thick was common. We noted soft drifts up to 3' thick along with substantial natural cornice failure, tender cornices, shooting cracks and several collapses.
The 2/2 Groundhog Day crust is buried 3' below the surface on SW aspects and 3.5' on NW aspects.
Despite a Winter Storm Warning, zero precipitation occurred during our tour.

Snowpack, Avalanche, Weather Images:

Travel Details

Region:

Swan Range - West Side (Flathead Valley access)

Route Description:

Activity:

Skiing

Snowboarding

Snowmobiling

Snowpack Details

Snowpack and Weather Details:

Terrain

Elevation of observation:

5000-6500 ft

Aspect(s) of observation:

Red Flags:

Shooting cracks

Collapsing / whumpfing noises

More than a foot of new snow or heavy snowfall rates (>1"/hr)

Blowing snow

Persistent Weak Layers:

Facets or Faceted Crust

Total Snow Depth:

100"

More comments about the snowpack and weather:

SW pit @ 5500' HS=70" ECTP 29 @ 33" below the surface on top of the 2/2 crust NW pit @ 6000' HS=100' ECTN 2/2 crust buried 40' below the surface

Blowing Snow:

Moderate

Wind Speed:

Moderate (Small trees sway)

Wind Direction:

Southwest

Air temperature:

Below Freezing

Snow line:

2000'

Sky Cover:

Overcast (OVC)

Highest Precipitation Rate:

No Precipitation (NO)

Avalanche Details

Avalanche Details:

Date and Time of Avalanche:

Tuesday, February 12, 2019 - 04:30

Avalanche Type:

Soft Slab

Failure Plane/Weak Layer:

Within storm snow

More information or comments about the avalanche:

Very small shallow storm slab avalanches on steep rollovers that occurred this morning prior to our arrival.

Trigger

Trigger:

natural

Terrain

Start Zone Slope Angle:

Starting Elevation:

near-treeline

Size

Destructive Size:

D1 Relatively harmless to people.

Relative Size:

R1 Very Small

Crown Height:

Less than 1 ft

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