Juneau Area Avalanche Advisory
2006-05-02
Juneau Urban Paths & Regional Notes
by Bill Glude, SAAC Observer
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While we were out doing fieldwork up Gold Creek a little before 5 pm today, the Snowslide Gulch Path across from the Perseverance overlook released a large slab avalanche that put a huge debris pile in the creek bottom. This path is often an indicator of the beginning of avalanche cycles.

We now have enough new snow to produce large avalanches that can reach lower elevations. The new snow depth is still relatively shallow, but it extends down to 300 m, allowing slides to continue to entrain more snow volume through mid-path. The volume produced makes for large, long-running slides.

Backcountry travelers should avoid avalanche terrain, limiting travel to small and less than 35° slopes, until the cycle is over. People should avoid the urban runout areas and minimize exposure time, especially below features like gullies that channel the main flow. This is NOT a good time to walk the Flume or run or bike down Thane Road.

Further snow load, wind transport, or rain to higher elevations is likely to trigger more slab avalanches in the area. Some could be large slides reaching the lower portions of the runout zones.

Also, note that there have been a number of large dry snow avalanches in the Haines area backcountry in the past two weeks. More information on that avalanche cycle is here.
Photos
Snowslide Gulch, Path J007 in Gold Creek, produced this large slab avalanche a little before 5pm today. We could not see the starting zone clearly enough to see if a cornice break triggered it, or if it was just due to loading from ongoing new and wind transported snow, or to snowpack stress from rain on the surface when a brief temperature rise occurred around 4:30.

The slab originated at about 950m, the top of the path. It appeared to only release about 60-70% of the starting zone. New snow this week has only been 35 cm at the Fish Creek weather station, probably no more than a half to a full meter in higher elevation drifted-in starting zones. But the slide entrained large quantities of new snow in mid-track, enough to produce a relative size 3 and destructive size 4 slide right to the creek bottom at 100 m.

The avalanche did not quite dam Gold Creek, as it sometimes does, but it piled debris at least 6 m deep and nearly 200 m wide. It was smaller than the usual late season slide on this path, but those are usually triggered in old corn snow, not fresh snow, and are 1 to 2 m deep, rather than 35 to 50 cm deep. This slide is remarkable for the volume and runout distance produced by a relatively thin slab.
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