West Brush Obs

Location: Brush Creek Area
Date of Observation: 02/19/2017
Name: Zach Guy
Subject: West Brush Obs
Aspect: North East, East, South East, South, South West
Elevation: 9,000-13,000 ft.

Avalanches: No new avalanches. Some cracking/storm slabs 2″ thick on the 2/17 near surface facet layer on NE aspects NTL; completely harmless but an indicator of how fragile that layer is right now.
See photos of older avalanches that ran during last storm or during the warm-up. Glide avalanches, persistent slabs, wet loose, and wet slabs.
Weather: Scattered clouds increased to overcast by late morning; S1 to S3 began around 12:30 p.m, about 2″ accumulation by late afternoon. Light SW winds with light snow transport at ridgeline. Mild temps.
Snowpack: Thick, supportive, frozen crusts on southerly slopes and no avalanche concerns on these aspects. Dry snow still on northerly aspects. The freshly buried 2/17 near surface facet layer was more pronounced/widespread on northerly near and below treeline slopes. Wind battered ATL here.  Didn’t see obvious signs of facets around the crusts on southerly slopes, except where the crusts were thin on low angle slopes. 3 pits on northeast aspects were as follows:
1) 10,500 ft. Thin melt-freeze crust about a foot deep, with 1mm facets below. Not reactive under current load (ECTN M) but something to keep an eye on.  Near surface facets 1″ deep.
2). 10,700 ft. 1/19 Surface hoar layer was 90 cm deep under a 1F slab. Propagating results in ECT with 4 additional shoulder hits beyond normal loading steps (ECTP 34, SC).  Near surface facets 2″ deep.
3.) 12,900 ft. A layer of small grained, well bonded facets was buried 45 cm deep. No fractures in a CT on any layers

Some recent and older glide avalanches. Easterly aspects BTL.

Some recent and older glide avalanches. Easterly aspects BTL.

D2. NE aspect N/BTL (10,700 ft). Looks like a natural from last storm, likely the buried SH layer but could have been a shallower weak layer.

Lots of wet loose activity on E, S, W aspects, averaging D1.5. This was a D2 Wet slab on S ATL, ran sometime during the warmup.

Several D1.5 and D2s on NE aspect NTL (10,700 ft and above). Looks like they ran last storm on the 1/19 SH layer, but could have been a shallower weak layer.

D2 on NE aspect N/BTL (10,700 ft). Looks like it ran last storm on the 1/19 SH layer, but could have been a shallower weak layer.

Buried rain crust/facet layer. NE aspect 10,500 ft.

Cracking and very shallow storm slabs on 2/17 NSF layer. NE aspect NTL

3 foot dense slab over propagating SH layer. NE aspect 10700 ft.