Back in the southwest flow

Location Name: 
Forecaster Observation - Cascade and Skiumah, Flathead Range
Observation date: 
Thursday, March 7, 2019 - 19:00
Is this an Avalanche Observation: 
Yes
Observation made by: Forecaster

Location

Tabs

Quick Observation

Skiumah Lake acts like a wind-tunnel during Southwest wind events so we went searching for wind slab issues there.  We found them. 

  • 2-3" of new snow, accompanied by increasing southwest winds (strong gusts) and moderate snow transport.
  • Above Skiumah Lake, we easily triggered numerous soft wind slabs on rollovers and crossloaded terrain features, generally 2-6" thick. A few were up to 1'.  These were all breaking on low-density storm snow that accumulated before the winds increased.  We also noted a handful of naturals.  All of these were small in size.  This problem was predictable and relatively easy to manage; we avoided terrain where a small slide would have bad consequences and steered away from features with the heaviest wind loading.  
  • We found minor wind effect in Cascade Creek, with good stability on all aspects, even near ridgelines.
Snowpack, Avalanche, Weather Images: 
Snowpack, Avalanche, Weather Videos: 

March 7, 2019: Fresh wind slabs above Skiumah Lake

Travel Details
Region: 
Flathead Range - Middle Fork Corridor
Route Description: 

Cascade to Skiumah Lake to about 6600'

Snowpack Details
Snowpack and Weather Details: 
Hide Terrain
Elevation of observation: 
3500-5000 ft
5000-6500 ft
Above 6500 ft
Aspect(s) of observation: 
N
E
SE
S
Red Flags: 
Shooting cracks
Blowing snow
Persistent Weak Layers: 
Facets or Faceted Crust
Buried
New Snow in the past 24 hours: 
2.00in.
More comments about the snowpack and weather: 
Exposed southerly aspects getting scoured back to the 3/5 sun crust. Wind slabs were stiffer at higher elevations, up to 4F. F+ hard a lower elevations. Breaking above us though, even in the softest slabs.
Blowing Snow: 
Moderate
Wind Speed: 
Strong (Whole trees in motion)
Wind Direction: 
Southwest
Air temperature: 
Below Freezing
Snow line: 
2500'
Sky Cover: 
Mostly Cloudy (BRK)
Highest Precipitation Rate: 
Very Light Snowfall (S-1)
Avalanche Details
Avalanche Details: 
Date and Time of Avalanche: 
Thursday, March 7, 2019 - 12:00
Avalanche Type: 
Soft Slab
Failure Plane/Weak Layer: 
Within storm snow
More information or comments about the avalanche: 

SE, E, or NE aspects. 

Hide Trigger
Trigger: 
skier
Trigger Modifier: 
Intentionally Triggered
Hide Terrain
Aspect: 
East
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): 
100ft.
Avalanche Width (Average width): 
30ft.
Hide People Involved
Number of people caught: 
0
Avalanche Location: 
Date and Time of Avalanche: 
Thursday, March 7, 2019 - 11:15
Avalanche Type: 
Soft Slab
Failure Plane/Weak Layer: 
Unknown
More information or comments about the avalanche: 

Fresh debris piles observed, likely WS that initiated just below corniced ridgeline

Hide Trigger
Trigger: 
natural
Hide Terrain
Aspect: 
Northeast
Starting Elevation: 
above-treeline
Hide Size
Destructive Size: 
D1.5
Relative Size: 
R1 Very Small
Avalanche Location: 
Date and Time of Avalanche: 
Thursday, March 7, 2019 - 15:15
Avalanche Type: 
Soft Slab
Failure Plane/Weak Layer: 
Within storm snow
More information or comments about the avalanche: 

One slide ran this morning, the other this afternoon.  The steep rollovers above the lake. 

Hide Trigger
Trigger: 
natural
Hide Terrain
Aspect: 
East
Starting Elevation: 
near-treeline
Hide Size
Destructive Size: 
D1 Relatively harmless to people.
Relative Size: 
R1 Very Small
Avalanche Length (Vertical Run): 
80ft.
Avalanche Width (Average width): 
30ft.
Avalanche Location: