Observation Date: 12/05/2019

Route/Location:
Seeley Lake area Southern Swan – Sunday Mountain to 7500′

Weather:
Cloudy skies with variable cloud ceiling between 6000-7500′. Very light snow showers at times. Temps above freezing to 6000′.

Wind:
Calm to light.

New Snow: 3-6″

Avalanche Activity:
None observed, other than small loose wet below 6500′, but visibility was limited.

Other Comments:
We experienced several collapses (aka “whumphs”) between 6500-7500′. We dug snowpits at 7150′ and 7400′ to further investigate collapses. Four snowpits and stability tests all yielded ECTP moderate (11-15) results with sudden collapse and sudden planar fracture character between 20-60cm down on very weak facets above the 11/17 melt-freeze crust. See the photos for further info.

Observer: Mat Brunton