Observation: Turnagain

Location: Tincan

Date:

March 31, 2017 4:00pm

Observer:

Johnston-Bloom/ Thamm Professional

Route & General Observations

Alternate skin track north of usual to 1700′. Standard up-track to 2250′. Checked out rain/snow line and overall stability including new snow/old snow interface, presence of melt-freeze crusts (rain and sun) crusts and buried persistent weak layers.

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)?	Yes
Cracking (Shooting cracks)?	No

Observer Comments

Recent avalanches observed along Seattle Ridge near Bertha Creek turn off.
Whumpfs/collapses at 1100' and 2250'
Localized cracking in wind affected snow, increasing length with wind exposure/elevation obviously upside down snow

Weather & Snow Characteristics

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

Weather

Cloudy skies, ceiling lifting on and off throughout the afternoon, fairly poor visibility. Did not get eyes on most of the Turnagain terrain.
Light precip, less than 1cm hr. Rain/snow line fluctuating around 1800'
Winds 10-20 mph with gusts into the 30s+.

Snow surface

Rain saturated to approximately 1800' tree bomb initiated roller balls, push-a-lanche conditions.
1800'-2000' damp surface snow
2000-2250' Wind skin/crust, grabby! Very noticeable wind effect as soon as skin track left the trees. Drifted and corniced along exposed features. Did not get into the alpine.

Snowpack

See corresponding pit photos. Facets and crusts present in all snow pits!

Hand pit @ 1200' NW
Snow pit @ 1550' NW, 23 degree slope, HS: 150, Height of pit 100 cm, storm snow: 50 cm over crust CT 12 ECTN 13, 3-4 mm surface hoar buried 55 cm from surface, CT 15, ECTN 17, 1 cm surface hoar buried 75 cm from surface, CT 25, ECTX. Both slab and faceted snow were F hardness. There was not enough of a slab to have propagation.

Snow pit@ 2200' SW, 25 degree slope, HS: 220, Height of 100 cm, storm snow: 45 cm over two layers of sun crusts over march facets, CT 24, CT 25, ECTX x 2 on upper sun crust. Similar snowpack to pit on SE aspect but no whumpfs or reactivity. Storm snow was very stuck to crusts. No propagation on the same facets found in
SE pit. Crust layers were a somewhat variable and discontiguous.

Snow pit @ 2250' SE, 30 degree slope. See pit profile photo. Two large whumpfs approaching slope, ECT failing on isolation on March facets. Spooky!

Photos & Video

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