Tour de Tunnel

Location Name: 
Forecaster Observation - Tunnel Ridge, Flathead Range
Observation date: 
Saturday, March 10, 2018 - 13:00
Is this an Avalanche Observation: 
Yes
Observation made by: Forecaster

Location

Tabs

Quick Observation

Toured into the Flathead Range to gather evidence on wind slab development and activity as well, monitor wet loose activity with today's warm temperatures.

  • Calm, bluebird day with temperatures rising to above freezing
  • Clouds moving over the crest during the morning kept temperatures from warming too quickly
  • Numerous natural, wind slab avalanches on northeast to southeast aspects primarily above 6500' (D1-D2.5)
    • One large natural wind slab ran approx. 3000' down to the valley bottom
  • Wet loose activity was slow to develop but came through with the afternoon heating and fewer clouds (between 1 - 3 pm)
  • Lots of rollerballs and pinwheels noted before wet loose action got going
  • Shady aspects held cool and dry snow all day at all elevations
    • Minor sluffing noted on shady slopes greater than 38 degrees
  • New cornice growth was easy to kick free but no natural cornice failures observed
Snowpack, Avalanche, Weather Images: 
Travel Details
Region: 
Flathead Range - Middle Fork Corridor
Route Description: 

Pinnacle to Tunnel Ridge up to 6800'.

Activity: 
Skiing
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: 
N
NE
E
SE
S
SW
W
NW
Red Flags: 
More than a foot of new snow or heavy snowfall rates (>1"/hr)
Rollerballs / pinwheels
Persistent Weak Layers: 
Not observed
New Snow in the past 24 hours: 
12.00in.
More comments about the snowpack and weather: 
Snow surface was warm and moist on sunny aspects at all elevations but stayed cool and dry on shady aspects at all elevations.
Avalanche Details
Avalanche Details: 
Date and Time of Avalanche: 
Friday, March 9, 2018 - 19:15
Avalanche Type: 
Soft Slab
Failure Plane/Weak Layer: 
New/old snow interface
More information or comments about the avalanche: 

Spoke with a group camping in Tunnel Creek. Their camp was located approx. 1500' from the toe of the debris associated with a large, natural wind slab. They said they heard the avalanche and felt the powder blast at their camp. Said the avalanche happen at approx. 7:15 pm on 3/9/2018. They hadn't noticed any evidence of natural activity when they skinned in on Friday during the day but woke this morning to find numerous crown lines on upper elevation, leeward slopes.

Hide Trigger
Trigger: 
natural
Hide Terrain
Aspect: 
East
Starting Elevation: 
above-treeline
Hide Size
Destructive Size: 
D2.5
Relative Size: 
R3 Medium
Avalanche Length (Vertical Run): 
3000ft.
Avalanche Width (Average width): 
500ft.
Hide People Involved
Number of people caught: 
0
Avalanche Location: 
Date and Time of Avalanche: 
Saturday, March 10, 2018 - 15:00
Avalanche Type: 
Wet Loose
Failure Plane/Weak Layer: 
Within storm snow
More information or comments about the avalanche: 

Numerous WL avalanches on west to east aspects, but the majority were confined to south aspects.

Hide Trigger
Trigger: 
natural
Hide Terrain
Aspect: 
South
Starting Elevation: 
above-treeline
Hide Size
Destructive Size: 
D1 Relatively harmless to people.
Relative Size: 
R2 Small
Avalanche Length (Vertical Run): 
500ft.
Hide People Involved
Number of people caught: 
0