Advisory Home
Previous Observation
Next Observation
Southeast Alaska Snow Discussion Group
Sample Advisory
Avalanche Danger Scale
Avalanche Photo Galleries
12-29-04 Juneau Rounds

We did the standard rounds of the urban paths this morning to see what may have come down and to check the loading and scouring from today's NNE winds.

We were concerned that the main Thane Road path, Snowslide Creek, might not have released already and that the windloading today might give it enough volume to reach the road. But it had already released sometime yesterday or early last night, producing the expected slide to low elevation but stopping short of the road at 10m. It cleaned out the weak layer on the SE side of the starting zone, so it is unlikely to slide again soon even though the fracture is already drifted in. The wind today is a little more northerly than our usual NE clear weather wind, so the unreleased side is not loading heavily. In fact, the wind has scoured to bare ground along and near much of the ridge.

The other urban paths are not heavily loaded, so may slide but will probably not reach lower elevations. The exceptions are J004 Chop Gully and J006 Sunshine paths, on the Gold Creek side of Mt Juneau, both of which are loading and have not yet released. It would not be wise to walk the Flume or ice climb in the runout of Sunshine today.

Most slab releases associated with Taku winds occur within the first 2 to 12 hours. Further wind at Taku strength usually does little to add to the load on the snowpack, as most of the snow goes into vapor phase in the dry Interior air before it lands.
Wind transport in the Twin Peaks area above Sheep Creek, looking toward the Taku River from Douglas at sunrise this morning. These outflow winds are caused by cold Arctic air spilling out from a high pressure area inland. They become strongest when there is a low offshore to create a strong pressure differential. The air channels through the valleys that form the only breaks in the mountain wall of the Coast Range. Our local river valley that cuts through the mountains is the Taku, and the strong clear weather winter winds down and near it take their name of Taku Winds from the river. The strength of such winds usually decreases with distance from the Taku River valley, but then picks up again beyond the Mendenhall Valley as northerlies blowing down Lynn Canal.
Yesterday's debris on T011 Snowslide Creek path along Thane Road. The debris has filled much of the area behind the diversion berm. The slide was a dry soft slab, new snow releasing on facets and faceted melt-freeze crust, naturally triggered by new and windloaded snow, relative size 3 and destructive size 3, and reached 10m elevation. The debris appears to be that of a wet slide because it encountered wet snow low in the runout zone. It was classified as SS-NO-R3-D3-I and the debris was estimated at 50 m wide and 0 - 8 m deep.