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Observation: Turnagain

Location: Tincan

Date:
Observer:
Route & General Observations

Toured up standard uptrack to ~2250′ (upper extent of treeline). Unable to tour above this point due to obstinate weather conditions. The creek at Tincan is freezing over again!

Red Flags
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Observer Comments

New snow and active wind loading due to strong winds

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

1200: 34 degrees at the road, variable light winds with moderate gusts, snowing <1"/hour, ridgetops obscured by clouds.
1400: 32 degrees at Center Ridge SNOTEL, variable moderate winds with STRONG gusts, snowing ~1"/hour, visibility under 1/4 mile.
1500: 34 degrees at the road, variable moderate winds with strong gusts, snowing ~1"/hour, ridge tops completely obscured by clouds. Rain / snow line was at ~700 ft elevation on the drive back to Girdwood.

Snow surface

2-6" of new snow, increasing with elevation, was found sitting on top of a completely (ski) supportable crust to ~2250' (unable to tour above this elevation). New snow was moist at lower elevations, but got increasingly dry near treeline. The near surface crust was ~2" at 2250', ~4" at 2150', ~6" or greater at 1000'. At 1800' and below, runnels were still quite visible underneath the newly falling snow. Above 2150' we found wind slabs forming on leeward aspects.

Snowpack

Our layer of concern was the Thanksgiving facets at the base of the snowpack. Additionally, we were interested in understanding the variability of the slab thickness, i.e., where does the snowpack transition from a 2' thick wet draining pack to a much thicker dry snowpack.

We dug a quick pit at 2000' and a more complete pit at 2250'. The height of snow averages ~100 cm at treeline, but can be extremely variable depending on wind loading (we found a range of a 55 cm to 185 cm in a short span on a wind affected feature). The quick pit at 2000' found multiple crusts in the upper 1/3 of the snowpack, with very moist snow in the midpack.

The pit at 2250' found interesting results on the Thanksgiving facets. The height of snow was 85 cm, but depth varied to 65 cm in the pit due to uneven terrain and wind loading. CT12 RP down 65 cm on 2mm moist facets, ECTP28 down 60 cm on 2mm moist facets, ECTP17 down 60 cm on 2mm moist facets, ECTX (likely didn't adequately isolate the column). These tests showed a dense slab, that included several layers of melt freeze crusts, that was failing in tests on the 5 cm thick Thanksgiving facet layer, sitting over a hard basal melt freeze crust.

We were also interested in determining where the near surface melt freeze crust ended. At our high point of 2250' we were still finding the near surface crust at 2" thick. Reports from a descending skier from the alpine, indicated that near the base of the ridge to Common Bowl on the standard uptrack, there still existed a near surface crust, as well as a fairly moist snowpack beneath the crust to the ground.

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