Crusts and Weak Layers in the Swan Range

Location Name: 
Forecaster Observation - Noisy/Jewel Divide
Observation date: 
Friday, December 7, 2018 - 15:45

Is this an Avalanche Observation: 
Yes
Observation made by: Forecaster

Location

Tabs

Quick Observation

Hiked up the Switchback trail and toured along the top of the ridge looking at the existing snowpack prior to the expected pattern change next week.

  • The snowpack sturcture is simialr to what we've seen elsewhere in the region. Below about 5,700' we found the buried crust from the storm that occured around Thanksgiving with facets below and very low density snow that is faceting on top. Above that elevation we found that the crust is much less pronounced. We saw 5-10mm surface hoar widespread on the shady aspects. We found a series of thin, weak crusts with low density snow in between on solar aspects.
  • The snowpack is generally stable for now. That will change if we get a slab on top.
  • We stomped on wind slabs that developed on the W side of ridges on Wednesday and found them unreactive.
  • We saw 2 recent sluffs, D1 in size, on sunny aspects in very steep terrain. 1 was skier triggered and 1 released naturally.
Snowpack, Avalanche, Weather Images: 
Snowpack, Avalanche, Weather Videos: 

20181207 - Looking toward the future

Travel Details
Region: 
Swan Range - West Side (Flathead Valley access)
Route Description: 

Up the road and Switchback Trail to the top of the ridge.

Activity: 
Skiing
Hiking
Snowpack Details
Snowpack and Weather Details: 
Hide Terrain
Elevation of observation: 
3500-5000 ft
5000-6500 ft
Aspect(s) of observation: 
N
NE
SW
W
NW
Persistent Weak Layers: 
Surface Hoar
Facets or Faceted Crust
On the surface
Buried
New Snow in the past 24 hours: 
0.00in.
Wind Speed: 
Calm (No air motion)
Air temperature: 
Below Freezing
Snow line: 
Valley floor.
Sky Cover: 
Partly Cloudy (SCT)
Avalanche Details
Avalanche Details: 
Date and Time of Avalanche: 
Thursday, December 6, 2018 - 12:00
Avalanche Type: 
Loose Dry/ Sluff
Failure Plane/Weak Layer: 
Within storm snow
Hide Trigger
Trigger: 
skier
Hide Terrain
Start Zone Slope Angle: 
45
Starting Elevation: 
above-treeline
Hide Size
Destructive Size: 
D1 Relatively harmless to people.
Relative Size: 
R1 Very Small
Crown Height: 
Less than 1 ft
Avalanche Length (Vertical Run): 
200ft.
Avalanche Width (Average width): 
30ft.
Avalanche Location: