Storm slab cycle in the Northern Whitefish Range

Location Name: 
Forecaster Observation - Red Meadow Lake, Whitefish Range
Observation date: 
Wednesday, December 12, 2018 - 18:15
Is this an Avalanche Observation: 
Yes
Observation made by: Forecaster

Location

Tabs

Quick Observation

Plenty of glaring red flags today at Red Meadow:

  • Widespread storm slab cycle, D1 to D2 soft slabs breaking ~1 foot deep on the near surface facet storm interface.  Most of these appeared to run this morning.  We observed slides in windloaded and windprotected terrain, all aspects and mostly mid and upper elevations.  Most of the debris stopped mid-track but some ran longer to Red Meadow Lake.  We also triggered several similar slides from a ridgeline; one was remotely triggered from ~30 feet away.  
  • We observed shooting cracks while ascending a moderately angled slope.  We also got several collapses as we neared the ridgeline into thicker, denser slabs.  There was about 12" - 14" of new snow at mid and upper elevations.  Strong westerly winds were drifting the snow at upper elevations.  We got easy, propagating results in an extended column test. 
  • Given all of these signs of instability, we kept to very dense trees or slope angles less than 35 degrees.   
Snowpack, Avalanche, Weather Images: 
Snowpack, Avalanche, Weather Videos: 

December 12, 2018: Storm slab cycle in the Northern Whitefish Range

Travel Details
Region: 
Whitefish Range - Northern (north of Coal Creek)
Route Description: 

Rode to Red Meadow from Polebridge.  Ascended Red Mtn to ~7200'

Snowpack Details
Snowpack and Weather Details: 
Hide Terrain
Elevation of observation: 
5000-6500 ft
Above 6500 ft
Aspect(s) of observation: 
E
SE
NW
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
Buried
New Snow in the past 24 hours: 
12.00in.
Total Snow Depth: 
110 cm
Blowing Snow: 
Moderate
Wind Speed: 
Strong (Whole trees in motion)
Wind Direction: 
West
Air temperature: 
Below Freezing
Snow line: 
2500'
Sky Cover: 
Overcast (OVC)
Highest Precipitation Rate: 
Moderate Snowfall (S2)
Avalanche Details
Avalanche Details: 
Date and Time of Avalanche: 
Wednesday, December 12, 2018 - 08:15
Avalanche Type: 
Soft Slab
Failure Plane/Weak Layer: 
New/old snow interface
More information or comments about the avalanche: 

Mostly mid and upper elevations

Hide Trigger
Trigger: 
natural
Hide Size
Destructive Size: 
D1.5
Relative Size: 
R2 Small
Crown Height: 
1 ft
Avalanche Length (Vertical Run): 
500ft.
Avalanche Width (Average width): 
100ft.
Avalanche Location: 
Date and Time of Avalanche: 
Wednesday, December 12, 2018 - 08:30
Avalanche Type: 
Soft Slab
Failure Plane/Weak Layer: 
New/old snow interface
Hide Trigger
Trigger: 
natural
Hide Terrain
Starting Elevation: 
above-treeline
Hide Size
Destructive Size: 
D2 Could bury, injure, or kill a person.
Relative Size: 
R2 Small
Crown Height: 
1 ft
Avalanche Length (Vertical Run): 
2000ft.
Avalanche Location: 
Date and Time of Avalanche: 
Wednesday, December 12, 2018 - 14:30
Avalanche Type: 
Soft Slab
Failure Plane/Weak Layer: 
New/old snow interface
Hide Trigger
Trigger: 
skier
Trigger Modifier: 
Intentionally Triggered
Hide Terrain
Aspect: 
East
Starting Elevation: 
above-treeline
Hide Size
Destructive Size: 
D1.5
Relative Size: 
R2 Small
Crown Height: 
1 ft
Avalanche Length (Vertical Run): 
700ft.
Avalanche Width (Average width): 
80ft.
Hide People Involved
Number of people caught: 
0
Avalanche Location: