Juneau Area Avalanche Advisory
2005-11-20
Mt. Troy
by Bill Glude, SAAC Observer
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This week's big tropical storm dumped record rainfall on Juneau, with 7.6 cm measured Saturday morning the 19th at Eaglecrest. Temperatures and snow levels soared while strong warm winds melted the snowpack, cutting the snow depth at 700 m in half. The snowpack warmed gradually though. We saw no avalanche activity from the thaw period.

Cooler air behind the front dropped the temperatures back down today. The snow level stayed near 350 m with moderate but steady snowfall.

We were out both days this weekend with the UAS Level I course. Saturday was soggy but rescue practice went well. Today was quite nice, snowy and a bit windy.

We found very few signs of instability. All tests showed a strong snowpack, stress was low, energy as indicated by poor shear quality, lack of shooting cracks, and high slab test scores was low, and the snowpack structure was strong. We did not note the tests individually on the profile because we were practicing in teaching stations. The students did a number of block tests, and most had no fracture.

Further thaw is unlikely to disturb this already-moist snowpack unless there is heavy snow and wind loading first. Cold weather would form facets over an ice crust. Heavy snow and wind could result in instability, but the new snow is relatively well-bonded to the rain crust at present.
Field Notes
Photos
The Friday night rains tapered off Saturday morning in time for our UAS Level I field trips. We found wet and mostly snowfree ground as high as Hilda Meadows, and only 15 cm of discontinuous snowcover at the Rescue Meadow (600 m). The night rains tapered to showers and the wind died, so we were able to do our rescue practice and return soggy but content with a good field day.
Today we found about 10 cm of new moist but smooth snow. It continued to fall moderately but steadily all day. Here we are doing a relay race observations game. The surface snow was slightly moist but good for traveling.
By the time we descended, the Rescue Meadow was still lumpy but transformed back into a wintry scene with steady snowfall continuing.
The snow turned wet at Hilda Meadows, but was accumulating right down to 350 m, below the Eaglecrest base area.
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