Juneau Area Avalanche Advisory
2006-03-23
Mt. Stewart
by Bill Glude, SAAC Observer
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We did fieldwork at Eaglecrest and on Mt. Stewart today. There has been widespread slab avalanche activity this week, most of it triggered by wet point releases or sluffs. The major cycle came on the afternoon of the 21st, the first really warm day of the spring. It was cooler and avalanches were less active today, but tests and field studies north of town yesterday showed ongoing thaw instability on warm days. Slides were most numerous on south and west aspects, but there were slides on other aspects as well.

Today remained cooler and the snowpack was stronger. The slush layer that has been triggering the slabs was frozen or semi frozen on most slopes in late afternoon. Activity is likely to resume when major thawing starts up again, it rains hard at starting zone elevations, or when we get a substantial new snowfall.

Backcountry travelers should take care to stay off and out from under steep slopes while they are going through their initial thaw and settlement period, at least through this week. Developed areas are not threatened by large slides until we get more snow.

Block tests today fractured on the first gentle jump or a second harder jump (AK4Q1, CAK4Q1, RB5Q2). Most were fast and clean Quality 1 shears. The Rutschblock fracture was fast like a Quality 1 but slightly incomplete like a Quality 3, so we gave it a Quality 2 rating.

With a thawed and wet 5 to 10cm surface layer yesterday, our blocks and test slopes released much more easily. Those surface layers had warmed but not changed into to melt-freeze grains on the NW aspect we tested today, and on nearby sunnier slopes the wetted surface layer was mostly frozen late in the day.

Our slab test results varied. The surface layer of new and weekend snow at our block test site, where it was not wind transported, scored a nonreactive #4. But last night's new snow scored a highly reactive #1 where it was freshly windloaded.
Field Notes
Photos
Most of the SW Face of Mt Troy released in a series of wet sluff-triggered slab avalanches over the last three days. These slabs are running as this week's new snow wets out and places creep stress on the underlying icy melt-freeze crust and sugary faceted grains that were on and just below the surface during the last clear spell.

The slides were most active on the 21st, the first really warm day of the season, and were less active today as cooler temperatures prevailed. They will resume with rapid warming.
These tracks leading to and from the bottom of the bowl are in the Hilda Creek drainage, coming over from the Dan Moller area. This bowl is a classic terrain trap, a bad-consequence place to be when wet slabs or large wet sluffs are running.
Mike Janes uses the snow sword to cut the back of our Rutschblock. It takes a meter-long saw like this one to effectively cut the back of the block full depth in snow containing even thin firm layers. Ski pole or shovel-mounted saws do not do an adequate job in anything but soft snow, and cutting cords leave an arch that usually fails to reach the layers the block is intended to test.
Bill Glude releases a fast clean Quality 1 shear on the Cutback AK Block on a first gentle jump on 41° (CAK4Q1). All our blocks went on the first or second jump today. In tests north of town yesterday when the snow was wet, not frozen, blocks and slopes released much more easily. Mike Janes photo.
Mike Janes uses collapsible ski poles to push across a too-flat traverse on his splitboard. The splitboard is a snowboard that comes apart into two skis when ascending and rejoins for the descent. It is a practical tool for field travel.

Snowboarders usually don't use ski poles because they get in the way on open slopes, but we already have them along for ascending with the splitboard, and we often find them very handy in rolling or gentle backcountry terrain.
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