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Observation: Turnagain

Location: Sunburst

Date:
Observer:
Route & General Observations

Standard West Ridge to 3500′

Red Flags
Red flags are simple visual clues that are a sign of potential avalanche danger. Please record any sign of red flags below.
Obvious signs of instability
Recent Avalanches?Yes
Collapsing (Whumphing)?No
Cracking (Shooting cracks)?No
Observer Comments

Some wind loading on SW aspects along ridge later in the afternoon as winds increased

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

Partly cloudy in the morning become mostly cloudy late afternoon
Winds were light in am becoming 15-20mph from NE
low to mid 20Fs
1-2cm of new snow from overnight

Snow surface

2" crust with trace of new snow on top at 1000'
6mm crust with 2cm new snow at 2300' - crust disappears by 2400'
surface hoar noticed around 2500' to ridge tops sitting on 5" loose snow

Snowpack

Dug 2 Pits at 2200' on WSW aspect about 50' apart and had very different structure. In one pit the MLK buried surface hoar was only 35cm below the surface and propagated with moderate force in two Extended Column Tests (ECTP15, ECTP17.) The slab was composed of 15cm of new snow on 1F-hard old snow. The other pit had 30cm of new snow on facets/sun crust with no propagation in Extended Column Tests. The MLK layer was found ~60cm below the surface and was well bonded, couldn't get it to sheer w/ sideways force.

Dug 2 pits at 4400' and 4450' on WSW aspect had similar structure. The new snow/old snow interface was 35-40cm below the surface and was mix of 1mm facts and 3mm buried surface hoar on 1cm suncrust. Stability tests failed constantly on this layer with moderate force (CT9, CT11x2, ECTP13, ECTP14, ECTP16, ECTP17.) The valentine's day facets were also found in both pits, but only failed in one CT. The MLK buried surface hoar was found in one pit 80cm below the surface and failed with moderate to strong force in two tests (CT17, ECTP29.) See pit diagram below.

The layer of most concern in our pits was the new snow/old snow interface that was first covered up on 3/7/19 by the first of three storms. We were also surprised to see the MLK layer reactive and showing propagation in two of 4 pits today.

Photos & Video
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