Observation: Turnagain

Location: Sunburst

Route & General Observations

Field Observations
January 24, 2013

Recent Avalanches-yes. Isolated pockets on Tincan Ridge. See photos.

1 Natural avalanche: SS-NC?-D1-R1. This avalanche was photographed from Sunburst
ridge at 2:45pm. It appeared to have been triggered by a chunk of cornice
falling onto the slope. There was no evidence of tracks near the avalanche and
reports from another observer lead us to believe that this was naturally
triggered. The starting zone had been in the sun for several hours at this
point in the day.
Approximate dimensions:
Crown width ~ 40′ across
Crown height ~1-2′
Vertical fall ~350′

1 skier triggered avalanche-SS-AS-D1-R1
This smaller “pocket” was photographed from the highway around 4pm. It occurred
sometime between 3-4pm. There is a ski track leading into the crown and it
appears the the person skied/rode off of the slab. This appears to be an
isolated wind slab that did not run very far. Rough dimensions are 20′ across
and 30′ down. Slab appeared to move less than 50′ down hill.

No Shooting Cracks
No Whoompfing

Surface observations:
1,000′-2,000′ : Supportable 2″ crust from with a trace of new snow on top
2,000′-3,500′ : Firm snow 3-5″ thick with 2-4″ of new snow on top
Pit results:
Elevation 2,000′
Height of Snow=160cm
The snowpack in this location contains several crusts. The warm temperatures of
the last several days were evident in this pit as several layers were at or
above 0 degrees C. The old (formerly faceted) grains at the base of the
snowpack at this site were rounded and smooth; very few sharp edges were
noticeable under the lens. The temp in this 25 cm thick layer was +.2 degrees C.
The take home point with this pit was that the weak base is gradually gaining
strength, due to very warm recent temps. When this layer freezes it should be
significantly stronger than it was a week ago.

Elevation 3,500′
Height of Snow=165cm
ECTN 18 28 cm down on 2mm mixed forms. Change in hardness at this interface was
from 4F (slab) to F (weak layer) hardness.
5cm layer of facets at the ground were Fist hardness, 3mm in size.
This pit showed us the weak base fully intact. This layer is currently non-
reactive to strength tests but is still a problem. We will continue tracking
this layer in many areas and elevations.
It was a low traffic day on Turnagain Pass. Tincan Ridge was the only area
between Girdwood and the Pass where we observed any recent avalanche activity.

Photos & Video
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