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Observation: Turnagain

Location: Seattle Ridge Up-Track, Repeat Offender

Date:
Observer:
Route & General Observations

The goal for the day was to get up Seattle Ridge and poke into the zones where two recent human triggered avalanches occurred yesterday, Feb 18.

Red Flags
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Observer Comments

None

Weather & Snow Characteristics
Please provide details to help us determine the weather and snowpack during the time this observation took place.
Weather

Very obscured skies with occasional waves of better visibility. Along the top of Seattle Ridge was difficult as visibility was consistently bad. Lightly snowing, winds very calm to none. Temperatures in the 20's F though it felt considerably warmer.

Snow surface

2-3" of low density new snow over all areas

Snowpack

We struggled to find a good place to dig a snowpit that would give us good information about the weak layer of buried surface hoar/near surface facets under last week's storm. A combination of low visibility and an inability to get onto any suspect slopes without putting ourselves or others in danger limited areas we felt comfortable digging.

We ended up digging 3 pits, one on the Seattle Ridge Up-Track at 2300', one at 2,800' just off the ridge down the face of Repeat Offender, and one in the trees between Main Bowl and Zero Bowl. Slab thickness (settled Valentine's Day storm total) varied from 1-3+' depending on wind scouring/loading. None of our pits yielded results at the old/new interface; under extreme force however (stomping or prying) we had 2 ECTP results at this layer. Under moderate force we were able to get some results at interfaces within the storm snow from last week, they did not snow much energy or propagation potential.

These results showed that the persistent weak layers of buried surface hoar and near surface facets we are concerned about are still present but are not necessarily reactive on all slopes. While this is good for some areas don't let it lure you into thinking all areas have this stability. There is still the potential to trigger a 2-3"+ slab in areas where the New/Old snow interface has not bonded well.

Photos & Video
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