Steamboat & Flat Tops

Avalanche

john morrone · Dec 26, 2017 · Steamboat & Flat Tops

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Weather

8400 feet elev near dry lake snotel and RAWS weather stations. broken clouds, 25F, nil wind, no precip

Snowpack

flat to N facing at 8400' within 1 mile of dry lake TH. hypersensitive failing MF crust near base of snowpack. travel was annoying to horrible, with ski pen of 60 cm ( on crust) to 90 cm (to ground), and boot pen to ground. poling and quick pit obs indicate 10-20 cm of basal facets under MF crust, with crust faceted away near rocks, shrubs or vegetation. This was covered by recent storm snow to 80-90 CM HS. travel only reasonable on only previous packed routes; trail breaking resulted in inconsistent support on MF crust with constant whoomphing and tree branch shaking up to 10 m distant. or skinning on rocks and dirt where MF crust was nonexistent (decomposed?). single significant steep terrain area had size 1 slab avalanche of new snow on basal facets.

Avalanche

sz 1, <tl, HS, N trig, N asp, R2, D1, either natural or remote trigger from 1-2 days previous. appeared to be wind slab on lee side of rocky ground, 40-42 degree at crown, 30-40 cm slab appeared to fail on facets, 60 feet wide, < 30 vertical feet, above commonly used ditchline trail. old track 10 m behind roll may have been a remote trigger.