Avalanches. Roller Balls. Mosquitoes?

Location Name: 
Forecaster Observation - Middle Fork
Observation date: 
Thursday, April 15, 2021 - 14:45

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

Tabs

Quick Observation

Quick trip in the Middle Fork to assess wet snow hazards.

  • The most recent round of loose wet avalanche activity began Wednesday afternoon on both south and north aspects at all elevations. One of these slides ran over ski tracks from earlier that day. South aspects had obviously been through more of a melt-freeze cycle. The snow on northerly slopes was still transitioning to wet and seemed even more unstable - probably the most dangerous aspects at the moment, at least at mid-elevations.
  • I easily triggered medium sized roller balls from my skin track and watched some natural rollers tumble down a steep south-facing slope around 11:30. I sank about 5 inches into wet snow with my skis on. Those clues told me it was time to turn around.
  • When I looked back up the canyon after my descent, I saw 3 new small wet loose avalanches on the same slope where I had seen the roller balls fall.
  • Large cornices are looming over steep northeast facing slopes on Nyack.
  • It was cloudy over the Divide, with fewer clouds north and west. Streaming clouds blowing east to west across the Flathead Range meant some slopes were getting full solar input and some were getting only transient sun.
  • Calm wind. Temperatures at the nearest weather station showed a high of 34 degrees at 5:00pm yesterday. It was showing 40 degrees by 2:00pm today.
  • Snow line is about 4,500 feet on south aspects and 3,800 feet on north aspects. Below that is patchy wet snow and occasional clouds of mosquitoes.
Snowpack, Avalanche, Weather Images: 
Travel Details
Region: 
Flathead Range - Middle Fork Corridor
Route Description: 
Activity: 
Skiing
Snowpack Details
Snowpack and Weather Details: 
Hide Terrain
Elevation of observation: 
3500-5000 ft
Aspect(s) of observation: 
N
NE
SE
S
NW
Red Flags: 
Avalanches from the past 2 days
Rapid or prolonged warming
Rollerballs / pinwheels
Persistent Weak Layers: 
Not observed
New Snow in the past 24 hours: 
0.00in.
Total Snow Depth: 
1 m
Blowing Snow: 
None
Wind Speed: 
Calm (No air motion)
Air temperature: 
Above Freezing
Snow line: 
Upper elevations
Sky Cover: 
Mostly Cloudy (BRK)
Highest Precipitation Rate: 
No Precipitation (NO)
Avalanche Details
Avalanche Details: 
Date and Time of Avalanche: 
Wednesday, April 14, 2021 - 17:00
Number of avalanches: 
3
Avalanche Type: 
Wet Loose
Failure Plane/Weak Layer: 
Old snow
More information or comments about the avalanche: 
Hide Trigger
Trigger: 
natural
Hide Terrain
Start Zone Slope Angle: 
45
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): 
300ft.
Avalanche Width (Average width): 
25ft.
Avalanche Location: 
Date and Time of Avalanche: 
Wednesday, April 14, 2021 - 18:00
Number of avalanches: 
3
Avalanche Type: 
Wet Loose
Failure Plane/Weak Layer: 
Old snow
More information or comments about the avalanche: 
Hide Trigger
Trigger: 
natural
Hide Terrain
Start Zone Slope Angle: 
48
Aspect: 
Northeast
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): 
400ft.
Avalanche Width (Average width): 
50ft.
Avalanche Location: 
Date and Time of Avalanche: 
Thursday, April 15, 2021 - 12:30
Number of avalanches: 
3
Avalanche Type: 
Wet Loose
Failure Plane/Weak Layer: 
Old snow
More information or comments about the avalanche: 
Hide Trigger
Trigger: 
natural
Hide Terrain
Aspect: 
Southeast
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 Location: