Avalanche: Turnagain

Location: Main Bowl, Seattle Ridge

Route & General Observations

APU Snow Science class traveled to Seattle Ridge to look at Main Bowl slide from yesterday.

Avalanche Details
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Trigger NaturalRemote Trigger0
Avalanche Type0Aspect North Northwest
Elevation 2300ftSlope Angle 37deg
Crown Depth2ftWidth 350ft
Vertical Run 400ft  
Avalanche Details

We took a good look at yesterday's slide in Mainbowl. HS - N - D3 - O.

We dug in at the left flank of the avalanche. The weak layer was 10 cm of fist hard facets 2.5 ft (80 cm) down. Bed surface was pencil hard melt freeze crust. Slab consisted of two parts, pencil hard rounds just above the facets, but the top half was softer. The debris was mix of up to refrigerator size hard blocks but also softer, smaller chunks.

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?No
Collapsing (Whumphing)?Yes
Cracking (Shooting cracks)?No
Observer Comments

Several whoomphs observed while traveling along Seattle Ridge between common uptrack and Main Bowl. One was very loud and propagated widely in a flat area, quick pit revealed 20 cm slab on top of 5 cm of advanced facets on bullet proof crust.

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

Bluebird sunburn kind of day at the pass. Temps 30s to 40s. No new snow. Calm in the morning, but wind picked up in the afternoon..

Snow surface

Morning travel easy skinning on supportable melt freeze. This corned up nicely for afternoon ski back to the van.
Time bring skin wax for tours with more moist surface snow.

Northerly snow surface stayed cooler and offered nice ski quality (in mellow terrain!).


We dug at several locations ENE and WNW aspects around Main Bowl. The weak layer of facets was consistently found at 80-120cm depths. This layer was stubborn and we did not get any test results (6 x ECTX & 3 PST no result), except one DT14@facet layer near the right flank of the slide.

Photos & Video
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