Fresh wind slabs will form in lee terrain features and below ridge crests. Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
Moderate to strong southwest wind will continue to build fresh slabs. Be especially mindful around steep and convex openings in the trees and ridge features in the alpine.
Cornices will continue to grow and might fail with the additional load.
A deeply buried weak layer has produced a number of large and surprising avalanches in the past two weeks. This problem is most likely to be triggered from thin or variable depth snowpack areas such as wind affected features, ridge crests, and near rocky outcroppings.
The same feature or path can slide repeatedly when the persistent weak layer gets reloaded with new snow.
Monday night: Mostly cloudy with flurries, moderate southwest wind with strong gusts, treeline low around -8 °C, freezing level below valley bottom.
Tuesday: Cloudy, 5 cm new snow, strong southwest wind, treeline high around -3 °C, freezing level rising to 700 m.
Wednesday: Cloudy, 20-30 cm new snow, strong southwest wind, treeline high around +1 °C, freezing level rising to 1000 m.
Thursday: Mostly sunny, trace of new snow, light southwest wind, treeline high around +4 °C, freezing level rising to 2600 m.
On Sunday, explosives triggered several avalanches of size 2 to 3. A few of these were persistent slab avalanches and released on the early December layer.
On Saturday, numerous storm slabs up to size 2.5 were triggered by explosives.
A natural avalanche cycle to size 2 occurred overnight Thursday-Friday with accumulating snowfall and wind. On Friday morning, explosives easily triggered storm slabs to size 2.5. Several natural slab avalanches of size 2 and one size 3 released naturally.
There has been an alarming pattern of large, persistent slab avalanches being consistently reported over the past two weeks. Almost all of these avalanches ran on the early December weak layer. Deeply buried persistent problems like these don't go away overnight, and it remains a serious concern.
15-30 cm of recent storm snow fell with southwesterly wind and warming temperatures, resulting in a denser slab forming over lower density snow. An accumulated total of 60-80 cm of new and recent snow now sits over variable and potentially weak snow surfaces including widespread facets, wind affected snow, and/or surface hoar up to 5 mm in sheltered areas.
The early December crust/facet layer has been responsible for sporadic but very large, persistent slab avalanches over the past two weeks. The crust is now buried 120-200 cm deep except in thin, wind affected areas near ridgetops where nearly all of the recent avalanches have been triggered.
