The load sitting on a variety of buried weak layers has reached a tipping point. If triggered, avalanches running on these weak layers will likely be large and destructive. Choose conservative terrain in the coming days.
A buried layer of surface hoar is now primed for human triggering. The slab rests on a persistent weak layer which has the capacity to propagate avalanches across terrain features. A crust that formed in November is near the base of the snowpack is also a concern for human triggering.
20 to 35 cm of new snow fell Monday night combined with moderate north and east wind. Watch for the formation of fresh sensitive slabs in the new snow that will likely continue to be sensitive to human triggering.
WEDNESDAY NIGHT: Mainly clear, light west wind, alpine temperature near -12 C.
THURSDAY: Mainly sunny, light southwest wind, alpine temperature near -5 C.
FRIDAY: Mix of sun and cloud, light southwest wind, alpine temperature near -4 C.
SATURDAY: Flurries, light southwest wind, alpine temperature near -3 C.
On Tuesday there were several reports of deep persistent slab avalanches running size 2-3 on southeast, east and northeast aspects. Three of these were size 2's triggered by skiers. Check out this MIN report from Tuesday afternoon for an example. As well, there were numerous size 1-1.5 explosives controlled storm slab avalanches.
During the day on Monday reports indicate a few explosives controlled size 1-2 storm slab avalanches in the north of the region.
On Sunday, avalanches to size 2 failed naturally and were sensitive to avalanche control measures. Reported avalanche activity primarily came from northeast, north and northwest facing features at and above treeline. This MIN highlights that activity nicely.
30 to 75 cm of storm snow has fallen in the past week with the deepest amounts being found in the north around Golden. Southwest winds have built slabs in lee features at upper elevations, reactive cornices have grown too.
Below the storm snow, the snowpack is a bit of a junk show. The early December surface hoar is down 30 to 80 cm below the surface now. On Saturday, before the big storm, it was sensitive to remote triggering which is well illustrated in this MIN post from the Golden area.
Below, or near the surface hoar you may encounter a crust. This crust can be bound as high as 2400 m in the south of the region and 1800 m in the north.
The lower snowpack is characterized by more crusts, the most notable is a rain crust from early November that is 50 to 130 cm deep. This crust is sitting near the base of the snowpack, surrounded by a weak layer of sugary facets. It is most likely to be reactive to human triggers or in a step-down from a smaller avalanche in shallow, rocky areas.
