Juneau Area Avalanche Advisory
2005-12-15
Mt. Stewart
by Bill Glude, SAAC Observer
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After about 10 to 20cm of new snow fell overnight above 600m, the snow level rose sharply today and light rain and warm SE wind began to thaw the top layers. We still have a net gain in snowpack thickness, though the sticky wetting snow surface made for slow travel today.

We did see some minor shooting cracks in drift areas and above our cutblocks, but otherwise the new snow slab did not show much energy storage. The trend is toward less energy because the new snow was moist to begin with and is wetting out gradually. There was a little SE windloading overnight and up to 20cm of new snow, both minor to moderate as signs of instability.

The only slope test results were the same shooting cracks in drifts and above cuts.

We did pit tests on the W side of Bunny Tow Pass on a 38° slope at 800m. Fog, wind, and poor visibility kept us from going higher.

The AK Block sheared on the bond we were concerned about in our last advisory, between the new snow and the underlying rime crust and near surface facets (now rounds). It went partially on the second, hard jump (AK5Q3). Only one of our three blocks fractured on that layer. The new snow is less sensitive because it is wetting out gradually, and skis sink through soft and thin new snow layers, making them test inconsistently.

All the other blocks sheared at fairly strong values on the same old surface hoar layer on top of facets at 23cm, now become moist melt-freeze grains, that our set on December 13 did. The AK Block and Rutschblock both went with average shear quality on multiple hard jumps (AK6Q2 and RB6Q2) and the cutback AK Block went on average shear quality on the first hard jump (CAK5). This layer continues to fracture in block tests a full week after hard rain fell on it and then turned to new snow, burying it deeply.

We judged the snowpack strength to be +, the stress to be ~, the energy to be ~, and the structure to be - (where + is an indicator of snowpack strength, - of weakness, and ~ neutral). Despite some loading and energy storage, the moist snowpack seemed to be settling and bonding rather than trending toward release.
Field Notes
Photos
About 10 - 20 cm of snow that fell overnight above 600m was being rained on today, but there has been a net gain in snowpack thickness so far.
Animals like this young porcupine were taking advantage of the mild wet weather to move.
The snow level was rising to over 800m today and warm wind was melting the snow on tree branches, frequently shaking it off onto the unwary traveler.
Our pit site at 800m on the West side of Bunny Tow Pass today featured fog, light rain alternating with slushy graupel, and winds gusting to 15 m/sec. But snow depth was suitable and we got in a good three-block test set on the 38° slope.

Only one test, the AK Block, sheared on the bond between the new snow and the underlying rime crust and near surface facets we had been concerned about in our last advisory. It went partially on the second, hard jump (AK5Q3). The new snow is soft and fairly thin, so skis tend to sink through rather than loading it, and it may be less sensitive because it is wetting out gradually.

All the other blocks sheared at fairly strong values on the same old surface hoar layer on top of facets at 23cm, now become moist melt-freeze grains, that our set on December 13 did. The AK Block and Rutschblock both went with average shear quality on multiple hard jumps (AK6Q2 and RB6Q2) and the cutback AK Block went on average shear quality on the first hard jump (CAK5).
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