A couple of problems are in play for the region. Seek sheltered terrain to avoid wind slabs and use careful snowpack evaluation and low consequence terrain to assess and manage the problematic persistent weak layer.
Cold, light, dry snow will begin to accumulate tomorrow afternoon with 10-20 cm possible. Moderate south winds with strong gusts are expected to drift this new snow into stiffer slabs on lee features at and above treeline, especially near ridge crests.
Two layers of surface hoar from late December are now buried 80-140 cm deep. Large avalanches breaking on these layers reported Wednesday give clear evidence that these persistent weak layers are still a concern.
Thursday night: Cloudy, scattered flurries with 2-5 cm of snow, moderate southwest wind, alpine temperature -16 C.
Friday: Cloudy, 10-20 cm of snow, moderate south wind gusting strong, alpine high temperature -10 C.
Saturday: Cloudy, 10-20 cm of snow, light south wind, alpine high temperature -9 C.
Sunday: Cloudy, 15-25 cm of snow, moderate south wind, alpine high temperature -10 C.
A widespread avalanche cycle occurred in the aftermath of the recent storm. Numerous large (size 2-2.5) and very large (size 3-3.5) avalanches released from natural, human, and explosive triggers in the storm snow and on deeper weak layers from late December across aspects and elevations. Persistent slab avalanches were breaking a meter deep, and one of them was remote-triggered.
Freshly formed wind slabs on Friday are expected to be reactive to human triggering and will have the potential to step-down to this deeper layer, forming large and destructive avalanches.
Low density snow will begin to accumulate tomorrow afternoon with 10-20 cm possible. Strong gusting south winds have the potential to drift this new snow into stiffer slabs on lee terrain features at higher elevations, especially near ridge crests.
The most recent storm delivered 40-70 cm of new snow across the region, burying two layers of surface hoar from late December down 80-140 cm deep. These layers continue to produce large to very large avalanches across aspects and elevations with continued loading from snow and wind.
