Observation: Turnagain

Location: Seattle Ridge

Route & General Observations

Partly cloudy skies (mostly alto-cumulus) with chilly temperatures (10-15F) and
calm wind.

Snow surface conditions:
There is around 2-4″ of low density snow from January 16th on the surface that
is faceting with the cold temperatures.

Below 1500′ – 2″ of the faceting snow from Wednesday (Jan 16th) sits on top of a
mostly supportable crust. Crust is from the last warm storm event ending 1/13-
Above 1500′ – variable wind affected snow with soft dense powder (good riding
conditions) in sheltered locations. Upper elevations have a harder wind affected
surface with a skiff of loose snow over the top in some areas.

Signs of instability:
Very small wind slabs being formed in exposed locations (6″ of less).
No avalanche activity seen or heard of since January 14th.
We were concerned about deep slab instabilities and keep slope angles

Snow pit test results:
Pit dug at 2,500′ and N facing. Snow depth 120cm (thin area).
– ECTP 28 sudden collapse, 105cm down in October facets.
– PST (propagation saw test) 35/100 End, Oct facets
– Deep tap test 19 sudden collapse, Oct facets
These are all red flag for deep slab problem. The October facets
were 3mm, dry and advanced. The slab is very hard, knife to 1 finger. Weak layer
is 10-15 cm thick and is the base layer of the pack. These results tell the same
tale we have been hearing for a while: “likelihood of triggering is low but
consequences are high”.
It is easy to forget this buried weak layer exists, unless you dig down to see
it or you hit the not-so-sweet spot and it avalanches big.

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