Quick report
- Red Flags
- Recent Avalanches, Wind Loading, Poor Snowpack Structure
- Red Flags Comment
- <p>Natural avalanche cycle from early week's wind event off the Ben Lomond/Willard Peak headwall. Most size 1 and 2 with crowns near the Skyline ridge; some well down off the ridge. Photo below. </p>
We dug many pits. You only need to dig a foot or two until you hit a stout crust from rain and warm temps in mid December. Maybe the 15th. At elevations below 7500 feet the snow got wet mostly from rain which switched to snow. Then temperatures got very cold and created a steep temperature gradient. 32 degrees F at the wet, rain soaked snow and temperatures approaching 0 degrees F or colder at the snow surface. This weather event (rain, snow and cold temps) was affected all aspects and seems to be more dependent of elevation.
However, this faceted layer produced consistent ECTN's (they would break but not propagate). Additionally it was very stubborn and would not crack or produce any alarming results in any informal tests. I was very surprised given how soft it is.
Most open slopes had small (2mm) surface hoar crystals. The next 2 days of high pressure will have perfect conditions for creating near surface facets as well. If this happens and this weak layer survives and is buried it may make the deeper layers irrelevant.
Images below are snow profiles from two different elevations. The first is from 6800 feet and all aspects at this elevation had this layering (N, S, and E). We did not investigate West, but it should be the same. The next image is from 7700 feet. Above this elevation, the facets were hard to find and almost non-existent. They produced ECTX results (ie-they would not break).
Photos:
- Mark Staples and Doug Wewer investigating the layering from the 12/27/16 human triggered wind slabs
- Example of natural activity off the Ben Lomond/Willard headwall from Monday night/Tuesday
- High pressure=junk in the valley, SH and near surface facets growing on the snow surface
- West to southwest winds and plumes off the skyline.
Snowpack
- Instability Comment
- <p>Hard wind slabs in many locations though none reactive to ski cuts or other prodding. West to southwest winds picked up just after noon with continued drifting above 8500'. </p> <p>Facets above the 12/15-16 rain crust remain something to keep an eye on and likely the culprit with naturals and human triggered slides on Cutler a couple days ago. Since, the snow has lost its sensitivity and will need rapid additional loading to reactivate this layer. This layer - as Mark indicated in his profiles - is most prevalent on all aspects but below roughly 7800'. </p> <p>Beyond that, the weakest snow is at the snow surface with SH and surface facets developing with the high pressure. </p>
Winds have touched most open slopes. The best powder was at lower elevations in the trees.
Small SH (2mm-) and likely recrystallized snow in protected terrain.