Observation: Turnagain

Location: Sunburst south face

Date:

November 17, 2012 12:00

Observer:

Wagner Professional

Route & General Observations

Went to take a look at the avalanche remotely triggered yesterday (Friday 11/16)
on the southwest face of Sunburst just below the weather station.
The original observation from 11/16 is below in the Obs list.

Avalanche details: (from both the party who triggered it plus ours from today)
Aspect: WSW
Elevation: 3700′
Slope angle: 40-43 degrees
Crown: 1-2′ (Slab was fist to 1finger hardness, right side up)
Width: 100-150′ that fanned/propagated to 300′ midslope
Length: ~1200′
Weak layer: October facets
Debris: 5′ deep with toe reaching valley floor 1-2′ deep.

Note: Sections of the crown showed the weakness was a thin layer of facets
above a thin melt freeze crust (possibly a sun crust from the end of October).
This MF crust was at the top of the October facets and can be seen in the crown
profile below. Some areas did not have this crust (see photo of crack).

Photos & Video

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Crown profile. Slab over weak facets with a thin MF crust between. Failure was just above crust (possibly sun crust from late October). Looking east.

Looking west at the crown

Cross section of a crack near the flank that did not avalanche. You can see where the slab collapsed then arrested in the top of the faceted layer.

Looking down the bed surface. Out of sight beyond the choke the slide widened to skiers left and ended up quite large.

A couple of snow pros asses the weak layer

Location

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