Juneau Area Avalanche Advisory
2006-04-30
Fish Creek Knob & Regional Notes
by Bill Glude, SAAC Observer
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Back from the spring American Avalanche Association board meetings in Wyoming, we got out to check the new snow today on Fish Creek Knob. Reports from Eaglecrest skinners yesterday said there were some naturals from all the snow and SE wind two nights ago, and windloaded pockets could easily be released. Today the snow seemed more relaxed but the 20 cm of new could be released with a skid on slopes as shallow as 38°.

The instability should settle out quickly as the snow bonds at these mild temperatures, but the ongoing snow and SE windloading forecast for the next few days could bring new instability. Late in the week, the forecast abrupt thaw could trigger a cycle on the melt-freeze crust at 169 cm.

Backcountry travelers should be cautious, choose terrain carefully, and expect slopes of 38° and steeper to produce slides as long as we are continuing to have rapid loading or abrupt thawing. These slides are not large enough to threaten developed areas, though natural releases are likely to reach the upper portion of the runout zones during the next cycle.

We have had ongoing reports of severe deep slab instability from heliskiers in the Haines area. There has been over 2 m of new snow over a probable surface hoar weak layer in the higher mountains there. Smaller human-triggered slabs have stepped out to 2 m depth and taken out whole faces recently.
Field Notes
Photos
The glades at 550m elevation looked more like December than the last day of April, with 20cm of fresh snow, more coming down steadily, and tree branches fully canopied with snow.
The new snow was moist enough to pack in and build snow stilts underfoot.
The view across the valley between snow showers showed more snow than we have seen most of the winter this year.
We were able to trigger the top 20cm of the snowpack on the slope adjacent to our block test site with a hard skidding stop turn on the 38° starting zone. The slide was a type intermediate between a slab and a point release, common in moist snow. It had the fracture line, bed surface, and shooting cracks of a slab, but stayed narrow and had flanks more like a point release.

Our tests showed a shear at this layer and slab tests were a fairly high energy 2, but all blocks produced only slow, irregular Quality 3 shears. So test results were mixed too.
Our block test site next to the ski-cut slide. We did five blocks and all sheared on the top 20cm with a sideways push of the ski at slow and irregular Quality 3 (AK2Q3, CAK2Q3, RB2Q3, CAK2Q3, AK2Q3). No other layers fractured.
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