Before the Storm

Location Name: 
Forecaster Observation-Swan Range
Observation date: 
Wednesday, January 5, 2022 - 16:15
Is this an Avalanche Observation: 
Yes
Observation made by: Forecaster

Location

Tabs

Quick Observation

We went to the Sawn Range to look for today's avalanche problem, and moreover, for conditions before the incoming storm.

  • We triggered one little wind slab on a northwest facing test slope around 6400 feet. Every other drift we encountered was stubborn to our stomping and stability tests..
  • In open terrain at middle and upper elevations, new snow will fall on low density fluff and soft drifted snow atop old hard wind slabs.
    • We were surprised how far downslope we felt hard, wind affected snow under the surface on all aspects. 
  • In sheltered terrain below about 6000 feet, and especially on scoured southerly slopes, new snow will fall on a thinner, weaker snowpack.
    • We found a very thin sun crust surrounded by faceting grains under the 3 inches of snow that fell last night.
    • There's another layer of small facets about 1.5 feet below the surface.
    • We got easy compression test results in these layers, but no propagation.
  • We looked for surface hoar everywhere but never found any.
Snowpack, Avalanche, Weather Images: 
Snowpack, Avalanche, Weather Videos: 

1/5/22 Before The Storm

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

To 6800 feet.

Activity: 
Skiing
Snowboarding
Snowmobiling
Snowpack Details
Snowpack and Weather Details: 
Hide Terrain
Elevation of observation: 
3500-5000 ft
5000-6500 ft
Above 6500 ft
Aspect(s) of observation: 
NE
E
SE
S
SW
W
NW
Red Flags: 
Avalanches from the past 2 days
Persistent Weak Layers: 
Facets or Faceted Crust
Buried
New Snow in the past 24 hours: 
3.00in.
Total Snow Depth: 
Over 2 meters
More comments about the snowpack and weather: 
Periods of blue sky (at least overhead) for the middle of the day. Increasing to obscured ahead of the incoming system. 3" HN overnight. S-1 snowfall began around 2:30pm. @5800 ft, SE aspect, HS = 110cm : 8cm HN over 1cm fragile sun crust from yesterday, NSFs above and below the crust, then 20cm 4F DFs over 15cm 1F- faceting grains. Tsurf = -8, T10 = -6.5, T20 = -5.5, T30 = -4. @6000 ft, 2 hasty pits on NW and SE. NW pit: CTE SP and ECTN9 down 10cm in NSFs under yesterday's sun crust. SE pit: CTM SC down 45cm in a deeper layer of NSFs. @6500 ft, 2 hasty pits on NE and SE, ECTNE and ECTNM and CTMs down 25 and 50 at interfaces between old wind slabs, CTH SC down 60 in 4F small FCs.
Blowing Snow: 
None
Wind Speed: 
Light (Twigs in motion)
Wind Direction: 
East
Air temperature: 
Below Freezing
Snow line: 
0 feet
Sky Cover: 
Increasing clouds
Highest Precipitation Rate: 
Very Light Snowfall (S-1)
Avalanche Details
Avalanche Details: 
Date and Time of Avalanche: 
Wednesday, January 5, 2022 - 12:00
Number of avalanches: 
1
Avalanche Type: 
Soft Slab
Failure Plane/Weak Layer: 
New/old snow interface
More information or comments about the avalanche: 

4F hard fresh slab from East wind failed on F hard recent snow. Bed surface was an older 1F hard wind slab.

Hide Trigger
Trigger: 
skier
Trigger Modifier: 
Intentionally Triggered
Hide Terrain
Start Zone Slope Angle: 
40
Aspect: 
Northwest
Starting Elevation: 
near-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): 
25ft.
Avalanche Width (Average width): 
25ft.
Avalanche Location: