Casca-Hoo-Cue

Location Name: 
Forecaster Observation - Middle Fork
Observation date: 
Sunday, April 11, 2021 - 15:45

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

Tabs

Quick Observation

Season closer in the Middle Fork was one of the better winter days, despite the calendar saying April. We stuck to terrain below 7000 feet; above that elevation it was obvious recent winds had affected the surface snow and created some a Wind Slab avalanche hazard. We found little evidence of a slab avalanche hazard on the numerous short, steep pitches we skied. These were up to 40 degrees, with one short, steeper pitch.

  • Above about 7000 feet, we saw evidence that recent winds had affected that near-surface snowpack: one small slab avalanche (avalanche details tab) and drifts in wave patterns across steep faces. 
  • Wind effects were isolated between 5000 and 6500 feet: some soft drifts, some scoured areas, and some 2-6" thick slabs inder several inches of new snow. Some of the drifted broke cleanly in hand pits, but we didn't find any cracking nor were we able to trigger short, steep test slopes. The thickest, slabbiest feeling snow was just on the downhill side of a convexity at 5200 feet. 
  • We triggered several small, harmless sluffs of new snow with turns on steep (>38*) slopes. These stayed in the surface snow and did not run fast. 
  • Cold temps and early clouds kept greenhousing on northerly slopes minimal above about 5000 feet. On sunny slopes and low elevations slopes, the 2-4" of new snow was wet and produced rollerballs while skiing. These did not coalesce into wet slides because there wasn't enough snow. 
  • Glide cracks an debris from glide avalanche exist on southeast-facing slopes. 

 

Snowpack, Avalanche, Weather Images: 
Travel Details
Region: 
Flathead Range - Middle Fork Corridor
Route Description: 

To 6900'

Able to skin from road into Cascadilla. Skis off 2x for Rescue exit. It was sporty. Mr. Toad's wild ride. 

Activity: 
Skiing
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
NE
E
SE
NW
Red Flags: 
Avalanches from the past 2 days
Rollerballs / pinwheels
New Snow in the past 24 hours: 
4.00in.
More comments about the snowpack and weather: 
Building clouds through the morning, with broken-overcast skies before noon. Almost no wind. A few brief flurries. Snow since 4/7 sits on a solid melt-freeze crust on all aspects and elevations where we traveled. Height of snow above crust varies with elevation, aspect, and wind exposure. 2-7 cm below about 5000 ft, except where drifted. Up to 30 cm on shady, upper elevations slopes. Generally ~one F-4F hard layer, but multiple layers where drifted, with a few scoured spots.
Blowing Snow: 
None
Wind Speed: 
Calm (No air motion)
Air temperature: 
Below Freezing
Snow line: 
4000'
Sky Cover: 
Increasing clouds
Highest Precipitation Rate: 
Very Light Snowfall (S-1)
Avalanche Details
Avalanche Details: 
Date and Time of Avalanche: 
Saturday, April 10, 2021 - 12:45
Number of avalanches: 
1
Avalanche Type: 
Soft Slab
Failure Plane/Weak Layer: 
New/old snow interface
Hide Trigger
Trigger: 
natural
Hide Terrain
Aspect: 
Northeast
Starting Elevation: 
7100 ft
Hide Size
Destructive Size: 
D1.5
Relative Size: 
R1 Very Small
Crown Height: 
Less than 1 ft
Avalanche Length (Vertical Run): 
200ft.
Avalanche Width (Average width): 
50ft.
Hide People Involved
Number of people caught: 
0
Number of partial burials: 
0
Number of full burials: 
0
Avalanche Location: 
Date and Time of Avalanche: 
Saturday, April 10, 2021 - 14:00
Number of avalanches: 
7
Avalanche Type: 
Loose Dry/ Sluff
Failure Plane/Weak Layer: 
Within storm snow
More information or comments about the avalanche: 

triggered with turns on steep north through northeast facing slopes. didn't run fast or far. Stayed on the surface.

Hide Trigger
Trigger: 
skier
Trigger Modifier: 
Intentionally Triggered
Hide Terrain
Start Zone Slope Angle: 
39
Aspect: 
Northeast
Starting Elevation: 
near-treeline
Hide Size
Destructive Size: 
D1 Relatively harmless to people.
Relative Size: 
R1 Very Small
Avalanche Length (Vertical Run): 
75ft.
Hide People Involved
Number of people caught: 
0
Number of partial burials: 
0
Number of full burials: 
0
Avalanche Location: