Observations

Turnagain

Observer: Fitzgerald / Wagner

Location: Tincan Trees

Date: Dec 25th, 2012

Touring in the Tincan trees today we experienced the following:

Obvious Signs of Instability:
-Recent avalanches-several short steep slopes had released naturally @ ~2000'
(stayed below treeline)
-2.5 ' crowns. Bed surfaces were filled in with 12" of new snow
-Shooting Cracks-mostly small, the biggest maybe 6 feet from skis
-Collapses-many, average size 50x50 feet?

Surface Obs:
Current Problems-
-unconsolidated surface snow-10-14" of fist hard snow made it hard to produce
obvious results on ski cuts and informal testing

Pit Results
-we dug to the ground and were able to see the new snow/old snow interface where
the avg HST=115cm (storm snow)
-ECTP14
-poor structure at the new snow/old snow interface down to the ground
-October/November snow showing some signs of strengthening but not enough to
feel confident in its ability to handle additional loading

Future Problems:
-concern for when the new slab condenses and behaves more like a slab
-pit results continue to show propagation potential
-slopes that are allowing the buildup of the new slab may take a longer time to
become reactive but will warrant respect for an extended amount of time
-while we may start seeing activity decline after peak loading, the problem of a
persistent weak base will require careful monitoring over time
-obvious signs trumped all pit data!

Over 3 feet of new snow for Christmas in Turnagain Pass. This has more than doubled the snowpack in less than 36 hours and is making for dangerous avalanche conditions over the holiday season.

Photo 1. Natual avalanche in the Tincan Trees - W aspect, 40 deg, 2,000'. 2.5 ft crown

Photo 2.

Lat: 60.7878 Long: -149.1670

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