Forecaster Observation - Cascadilla Creek, Flathead Range

Location Name: 
Forecaster Observation - Cascadilla Creek, Flathead Range
Flathead Range - Bob Marshall Wilderness
Date and time of avalanche (best estimate if unknown): 
Wed, 03/15/2017 - 12:00
Location Map: 

Red Flags: 
Recent avalanche activity
Obvious avalanche path
Terrain Trap

Observation made by: Forecaster
Avalanche Observations
Avalanche Type: 
Trigger type: 
Number of similar avalanches: 
More than 10
More detailed information about the avalanche: 

The focus of todays tour was to determine the size and distribution of avalanche activity associated with the March 15 warm rain event in Cascadilla Creek in the Flathead Range. My other objective was to determine the state of the crust at the snow surface at all elevations.

  • Numerous wet loose avalanches, which ran long distances, were noted at both mid and upper elevations on all aspects.
  • Numerous slab avalanches were observed at mid elevations on southeast through northeast aspects. Several slabs were observed on northwest aspects. The majority of these appeared to be several feet deep and probably failed on the February 9 and 17 rain crust. The destructive potential of most of these were D2-D3.
  • A number of slab avalanches were observed at upper elevations on southeast through northeast aspects of Nyack Mountain, Most of these did not appear to be as deep as the mid elevation slabs and possibly failed as a storm slab. There were a couple of instances where a storm slab released which then stepped down to a deeper layer (February 9 and 17 rain crust). These latter slides had a destructive potential of D4 which means that these slides had the potential to destroy a railway car, large truck, several buildings, or a substantial amount of forest.
  • In the morning the snow surface at low elevations was not supportable to skis but the mid and upper elevations were. By early afternoon all elevations that were receiving sun were unsupportable to skis. When I exited the upper basin mid and upper elevations that were not receiving direct sun remained supportable to skis. I did not encounter any surfaces that were able to support boot packing throughout my tour.  Today's crust varied between 1' at low elevations to 4" at upper elevations. This crust capped a thick layer of moist snow at all elevations.
Avalanche Photos: 
Weather Observations
Cloud Cover: 
25% of the sky covered by clouds
Air temperature: 
Above Freezing
Air temperature trend: 
More detailed information about the weather: 

Mostly cloudy in the morning followed by a bluebird afternoon. The mid March sun was intense and softened the snow surface relatively quick when skies cleared.