Forecaster Observation - Wahoo Ck vicinity, Flathead Range

Location Name: 
Forecaster Observation - Wahoo Ck vicinity, Flathead Range
Region: 
Flathead Range - Bob Marshall Wilderness
Date and time of avalanche (best estimate if unknown): 
Tue, 02/07/2017 - 16:00
Location Map: 

Red Flags: 
Recent avalanche activity
Recent loading by new snow, wind, or rain
Obvious avalanche path
Observation made by: Forecaster
Avalanche Observations
Avalanche Type: 
Dry
Slab
Trigger type: 
Natural
Aspect: 
Northeast
Terrain: 
Near Treeline
Elevation: 
5 900ft.
Avalanche Length: 
2 500ft.
More detailed information about the avalanche: 

An avalanche was reported to have reached the BNSF railroad grade at approximately 0400 on February 7, 2017. FAC staff investigated the runout zone of this slide on the afternoon of February 7. The crown of the avalanche was not investigated due to the dangerous avalanche conditions present. At the time of the avalanche the Flathead Range was under an Avalanche Warning.

  • The avalanche occurred in an unnamed drainage between Cascadilla Creek and Wahoo Creek.
  • Upon investigation, this slide had crossed the rail grade and terminated on Highway 2.
  • The railroad grade was in the runout zone of this avalanche path and 275 linear feet of the rail was affected. 125 linear feet received the brunt of the debris which reached a depth of 5 feet.
  • We are assuming the avalanche traveled approximately 2500 vertical feet.
  • There is a power line that crosses the bottom of the avalanche track which was damaged by debris disrupting the power supply.
  • A number of spruce and cottonwood trees were knocked over by the debris. Most of these were 20-30 feet tall and up to 14 inches in diameter.
  • Evidence of the powder cloud, that preceded the debris, reached 35+ vertical feet in trees between the rail and highway.
Avalanche Photos: 
Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
50% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Light (Twigs in motion)
Air temperature trend: 
Static
Wind Direction: 
Southwest