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Observation: Turnagain

Location: Tincan

Date:
Observer:
Route & General Observations

Field Observations
December 18, 2014

Route
Tincan up to top of Common Bowl

Weather
Temps in the low 20’s
Winds calm
Sunny clear skies, no precipitation

Obvious Signs Of Instability
Recent Avalanches-YES – Skier triggered avalanche on Sunburst SW face (see Avalanche Report)
-Natural avalanche on SW face of Kern (picture below)
Shooting Cracks-NO
Collapsing – Localized collapsing at 2300′

Surface Obs
1000′ – 2” new snow on 1″ crust on ground.
1500 – 2000′ – 10 – 25” new snow from Dec.14-17 storm
Above 3000′ – 20 – 35” new snow from Dec.14-17 storm

Snow Below the Surface
This new snow is sitting on a layer of buried surface hoar that appears to be very wide spread and has been found at all elevations above 2000′. This weak layer is laying intact on the Dec.7-9 rain crust. This rain crust disappears at about 3000′, but buried surface hoar has been found on the old snow interface at higher elevations. Meaning its all over the place.

Pit @ 2300′ – 53″ (135cm) total snow depth, WSW 25* slope. 25″ (60cm) of new snow on top of 1/4 -5/16″
(6-8mm) of buried surface hoar sitting on a moist Dec.7-Dec.9 rain crust. Within the new snow there was
two rain crust layers stacked on top of each other about 11″ (30 cm) from the surface. (See photo below)
We dug two pits and did 3 test with scores of ECTP17, 20, 23 SC (Q1)

Pit @ 2700′ – 57″ (145cm) total snow depth on an W aspect, 25* slope, 28″ (70cm) of new snow on top of
1/8-5/16″ (3-4mm) buried surface hoar sitting on Dec.7 – Dec.9 rain crust. Within new snow there was a
thin 3/8″ (1cm) rain crust about 16″ (40cm) from the surface. ECTP22, 23 SC(Q1)

Pit @ 3400′ – 114″ (290cm) total snow depth on a SW aspect, slope, 35″ (90cm) of new snow on top of 1/8-
5/16″(3-4mm) buried surface hoar sitting on an old snow interface. We had an ECTP20 SC. The test failed
at 35″ (90cm) down on buried surface hoar and it also failed at 16″ (40cm) on a new snow hardness
change. Both failed on the 20th tap.

This is a very scary snow pack right now. The unstable persistent weak layer of buried surface hoar seems
to be wide spread. Today natural avalanches, remote triggers and a human triggered avalanche have all
been observed from Girdwood all the way to Summit Lake. Due to how deep the slab is on top of this weak
layer it may be difficult to trigger. Be weary of any steep slopes above 35* that have already been skied. It
very likely that the second or fifth person on the same slope could trigger a large avalanche. Be
conservative in your route selection and avoid traveling in the run out of steep terrain. Keep your slope
angles below 35* until this layer proves itself innocent.

Photos & Video
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