Weak snow in Canyon Creek

Location Name: Forecaster Observation - Canyon Creek, Whitefish Range Observation date: Sunday, December 9, 2018 - 12:30	Is this an Avalanche Observation: Yes

Observation made by: Forecaster

Location

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Quick Observation

Instabilities observed on our tour were confined to the surface snow. 3 small dry loose natural slides were noted on mid-elevation steep north aspects. These appeared to have run in the past 48 hours. We were able to intentionally trigger dry loose sluffs on steep south facing slopes at mid-elevations. These sluffs entrained all of the loose surface snow which ran on top of a suncrust
Ridgeline locations showed evidence of recent wind loading and fresh cornice development. Both were unreactive to ski stomping.
A well preserved layer of surface hoar was noted on north facing aspects at upper elevations. This layer may become troublesome after a load is put on it.
An overall weak thin snowpack was observed in the southern Whitefish Range.

Snowpack, Avalanche, Weather Images:

Snowpack, Avalanche, Weather Videos:

December 9, 2018: Weak Snow in Canyon Creek

Travel Details

Region:

Whitefish Range - Southern (south of Coal Creek)

Route Description:

Traveled the ridge on the north side of Canyon Creek.

Snowpack Details

Snowpack and Weather Details:

Terrain

Elevation of observation:

5000-6500 ft

Above 6500 ft

Aspect(s) of observation:

Persistent Weak Layers:

Surface Hoar

Facets or Faceted Crust

On the surface

Buried

New Snow in the past 24 hours:

0.00in.

Total Snow Depth:

36"

More comments about the snowpack and weather:

Sunny aspects harbored 2 or more sun crusts, loose faceted surface snow and facets on either side of the crusts. Our snowpit on a north aspect at a ridgeline elevation revealed a right side up snowpack which transitioned from 1F hard near the ground to F hard at the surface. A well-preserved surface hoar layer, formed around Thanksgiving, was 14" below the surface. This layer failed during compression tests with moderate force. No propagation was observed with this layer during multiple ECT tests due to the soft nature of the overlying slab.

Wind Speed:

Calm (No air motion)

Air temperature:

Below Freezing

Snow line:

2000'

Sky Cover:

Overcast (OVC)

Avalanche Details

Avalanche Details:

Date and Time of Avalanche:

Saturday, December 8, 2018 - 15:30

Avalanche Type:

Loose Dry/ Sluff

Failure Plane/Weak Layer:

New/old snow interface

More information or comments about the avalanche:

Faceted loose snow surface failing at a density change.

Trigger

Trigger:

natural

Terrain

Start Zone Slope Angle:

Aspect:

North

Starting Elevation:

near-treeline

Size

Destructive Size:

D1 Relatively harmless to people.

Relative Size:

R1 Very Small

Avalanche Length (Vertical Run):

50ft.

Avalanche Width (Average width):

5ft.

Avalanche Location:

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Weak snow in Canyon Creek

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December 9, 2018: Weak Snow in Canyon Creek

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