Juneau Area Avalanche Advisory
2005-12-27
Mt. Stewart
by Bill Glude, SAAC Observer
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We went up Mt. Stewart today to see how the new overnight snow and incoming storm were interacting. Since the lower portion of the snowpack is quite solid, we only looked at the 5 to 15 cm of new and windloaded snow. We could test those layers with observations and slope and traveling tests, without digging snowpits.

Overnight snowfall was light, but there was a dusting down to at least 300m. In the morning as we began our fieldwork, it began to snow and the temperature warmed. On the upper slopes, we found up to 15 cm of recent snow in the drifted areas. On the summit, it was -1°C with winds in the SE 0-15 m/sec range.

The snow was dry in the morning and sensitive in the windloaded areas. Our observations included minor shooting cracks and still-light but increasing new snow and windloading. Our slope and traveling test results included some cracking between and around our skis, one mini-slab on a test slope, lots of skin slippage on the underlying crust, and sensitive slab test results (Slab #2, taking out most of the undermined area quite cleanly). We judged the strength -, the stress +, energy -, and structure -, where + indicates a stronger snowpack, - weaker, and ~ neutral, but the amount of new load was still small enough for there to be only some small thin unstable areas.

By afternoon, instead of building toward greater slab instability, rising temperatures were beginning to slowly wet the snow below 750m so it trended toward small wet point releases and many cinnamon roll snowballs. We judged the strength ~, the stress +, the energy +, and the structure ~.

As we descended it continued to warm, continuing the trend we saw during the day. Snow levels seem to be fluctuating widely in the storms we are getting this week. The icy crust that was suspect today under the recent soft snow will remain weak until it either wets out thoroughly or has some time to bond to the overlying snow. Instability will depend largely on new snow and windloading amounts.

In regional snowpack news, we have a report from Bruce Bauer of Mosquito Lake, 28 miles north of Haines, saying it's pretty thin at his place but that the skiing and snowmachining up on the Haines Pass is now quite good. So it you're looking for some good snow in the area this week, head north!

Field Notes
We did no pit studies today. There was only 5 to 15cm of new snow over a firm, settled base. We were able to use slope and traveling tests to evaluate conditions without taking out our shovels.
Photos
We were surprised to find a water ouzel, or dipper, foraging happily at 650m at the bottom of the NE Bowl. The open water here usually disappears under snow and ice from mid-November through mid-April.
Fog and blowing snow limited visibility on the upper slopes today. Descent required intimate familiarity with the terrain and ability to ride by feel in whiteout conditions.
Slab tests in the morning showed sensitive snow in the wind drifted spots. Here, most of the undermined area has broken out quite cleanly, a Slab #2 on our test scale. By afternoon, rising temperatures began to slowly thaw the snow and cinnamon roll snowballs and small wet point releases dominated instead of the slabs that were starting to build in the morning.
A small test slope on a steep windloaded roll produced this mini-slab when jumped on in the morning. Only the top windslab layers fractured here, but our slipping climbing skins showed that the bond of all the new snow to the underlying icy melt-freeze crust remained weak.
By afternoon, especially below 750m, rising temperatures began to wet the surface layers, producing classic indicators like the snow plug sliding ahead of our right ski.
Turns below 750m in the afternoon as the snow wetted triggered small wet point releases and released lots of cinnamon roll snowballs.
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