Observation: Turnagain

Location: Silvertip Creek

Route & General Observations

Feb 25, 2013

Silvertip Creek

Weather: Temps in the mid 20s F, light SE winds, no precip, overcast/scattered

No recent avalanches observed
Several large collapses (~60 ft diameter) @ 1,200′
No shooting cracks

Surface obs: 2-18″ new snow sitting on a crust.

Pit results @ 1,200′, NE aspect (see video)
After experiencing collapsing we stopped to investigate the cause. We dug in a
lightly windloaded spot that had 14-18″ of storm snow sitting on a crust that
formed on 2/22.

Test results showed:
Moderate strength
High propagation potential
Poor structure

ECTP 10-15
PST 25-30/100 (End)

A thin crust (~1cm) has a slab above it and a very thin layer of weak faceted
snow (mixed forms) below it. Below that layer of weak snow is a thick and stout
layer of melt freeze grains (crust).

Based on collapsing and pit results that correlated with an assessment of
unstable snow we turned around.

We then drove to Turnagain Pass and dug at a similar elevation at the base of
Magnum. We found a very similar structure but no collapsing or results at this
crust/storm snow interface.

The results we had at Silvertip today fall into the ‘outlier’ category in terms
of the overall snowpack picture in the forecast area. This is a lower elevation
problem that we will keep an eye on. It does not to appear to be an issue on
Turnagain, despite the similar snowpack structure.

Photos & Video
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