Today's day off ski tour took us into the Flathead Range to seek out good views and powder skiing. Not only did we achieve those, but we also got to observe the aftermath of a D4 avalanche off Nyack.
Our best estimated time of occurrence was Sunday night or Monday morning, 6"-8" new snow on the bedsurface. We estimate the crown height ranged from 5 to 15 feet deep. Avalanche snapped mature trees. Debris terminated past previous tree line. Measured alpha angle at 20 degrees. Powder cloud extended deep into the forest, several hundred yards past the trim line.
This debris pile had a trace of snow on it which makes us believe it occurred sometime late yesterday or last night. Multiple mature trees were in the debris. Debris terminated at the right flank of debris pile from the D4.
Unknown if this was a wind slab or sluff due to far view. Evidence of cross loading into the gully it ran out of. No observed crown.
Roadside observation into Cascadilla drainage. Unknown width and verticle run. Failure date could be anytime in the past few days.
Skied over this debris pile, the debris was buried by 15" to 18" of new snow. Unknown avalanche character. Similar debris piles seen from afar but too far away to document with confidence.
