Southern San Juan

Avalanche

Kit Barton · Feb 1, 2021 · Southern San Juan

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Weather

beautiful day. cold morning warm day. dead calm. solar aspects developed a thin sun crust as the afternoon cooled. snow was surfy pow.

Snowpack

Pit at 11,200' on a SE aspect 50 feet below ridgeline. HS 75cm. Shovel shear easily peeled off the slab at the new snow/old near surface facets interface (4F), around 30 cm (estimated, forgot to measure depth of failure). below this was a 10 cm thick (1F) melt freeze crust from the extended dry period a few weeks back. Below that were well developed basal facets (4-6 mm). Saw propagation test on the same interface as the ECT failed 10 cm into the column. Q1, if our pit had been on a steeper slope it would have slid right off. The facets between the new snow/old snow were quite strong in compression, extremely weak in shear.

Avalanche

D2.5 natural on the peak east of Snowden. NW aspect, broke midway down the bowl and ran a ways into the trees. Likely wind slab from SW windloading. Numerous D1 - D2 wet loose on solar aspects, especially below rock bands on the ridge between Kendal and Whitehead, those ran in the afternoon of 1/31. Older (1/29?) D1.5 E facing slab north of Whitehead. Maybe was storm slab that ran during the storm.