Observation: NWAC Observer

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Weather Summary

Calm, clear, and cold

There were signs of old roller balls and wet loose debris from the warm up on Wednesday and Thursday (1/25 - 1/26). This older debris has several inches of snow covering it.

Snowpack Observations

The skiing was not fantastic overall, but we did find some fun shallow snow on crust near tree line. Near Washington Pass there is small 1-2mm needle surface hoar covering the 6" of new-ish snow which is lightly faceted. This may matter when new snow falls.

As we ascended through tree line the wind effect became apparent and the recent storm snow varied in depth on top of the recent crust. By 6500' There was a 1-3" wind slab on the surface which was noticeably harder than the soft snow below. By 6700' we found ourselves at the edge of a small pocket where the wind slab was 18". We turned around here. The transition from a 2" slab to an 18" slab was pretty sudden; a good reminder of just how variable wind slab can be in depth and distribution.

Moving into safer locales we dug a pit at 6400' on a South aspect to see what's going on. A description of the layers is below. We performed an extended column test which produced a failure just above the MLK crust (ECTP 24 @ 47cm). This is about 20" down. The snow above the crust is faceting with the cold temps, but there haven't been signs of avalanches on this layer during or since the mid week warm up. Also, a propagation saw test we did on that layer indicates unlikely propagation (PST 58/100 down 47cm). This seems like a layer to keep an eye on when new snow or other changes come along. We did not observe the 1/5 buried surface hoar layer where we were (S facing above tee line).


Overall height of snow varied from 170 to 230cm


Layers from the top down:

Surface-15cm: Decomposing fragments , 4 Finger hard

15-17cm (1/27 crust): Melt Freeze crust, pencil hard

17-48cm: Faceted crystals, 1 finger hard

48-55cm: (MLK crust): Melt freeze crust, pencil hard

55-80cm: Faceted rounded particle, pencil hard

80-105 (Xmas crust): Melt freeze crust in tiger stripe layers, pencil hard

105-205: snow to ground (we did not dig below Xmas crust)

A link to the Snow Weather and Avalanche Guidelines if you find snow crystal descriptions and snowpack tests interesting: https://www.americanavalancheassociation.org/swag

Avalanche Problems

Problem	Location	Distribution	Sensitivity	Size	Comments
Wind Slab	N E S W	Isolated Specific Widespread	Unreactive Stubborn Reactive Touchy	D1 D1.5 D2 D2.5 D3 D3.5 D4 D4.5 D5

The wind slab above treeline seems to be the only avalanche problem at play right now, but lets keep an eye on upper snow pack crusts/ layers.