Triggering large avalanches remains likely in wind-drifted snow or on open glades near treeline where a buried weak layer persists. Persistent slab avalanches can travel far and can be difficult to predict, so a conservative approach is recommended.
Ongoing ridgetop winds have redistributed recent low density snow into wind slabs on lee features at upper elevations that remain reactive to human triggering.
A weak layer of surface hoar is buried 80-130 cm deep on sheltered slopes near and below treeline. This layer continues to be reactive to human triggers.
Brrrrrr! Cold and dry conditions persist under arctic air
Monday night: Mostly clear, light northwest wind, alpine temperature -23 C.
Tuesday: Clear, light variable wind, alpine high temperature -18 C.
Wednesday: Mix of sun and cloud, light northwest wind, alpine high temperature -20 C.
Thursday: Mainly sunny, light northeast wind, alpine high temperature -23 C.
A natural cycle of large (size 2-2.5) wind slab avalanches were reported over the weekend. These avalanches released on north through east through south aspects above 2000 m and broke 30-80 cm deep. A few of these wind slabs were triggered by cornice falls. In this MIN from London Ridge, observers reported a very large wind slab avalanche that may have stepped down to a deeper layer.
Reports of human-triggered avalanches breaking on the late January surface hoar continue to trickle in. These avalanches have been primary occurred in the near treeline elevation band. However, this MIN report and this MIN report from over the weekend are helpful examples of how cutblocks or "treeline-like" features that are below treeline have caught groups off-guard. This MIN report from last week near Kokanee Pass offers a sobering look at the potential for this problem to propagate widely across features.
Numerous small (size 1-1.5) loose dry avalanches in unconsolidated snow have been reported in steep terrain.
Up to 45 cm of low density snow over the past few days has combined with moderate northwest winds to create wind slabs which may remain reactive in lee features. In sheltered areas, cohesion-less powder may be prone to dry loose avalanches that can run far and fast in these cold, dry conditions. With clear skies, steep slopes in direct sun may rapidly warm midday despite the cold temperatures, and sun crusts may develop.
80-130 cm of snow from the past week is settling over a weak layer of surface hoar that has shown reactivity at treeline or in "treeline-like" features below treeline. This persistent weak layer has potential to surprise backcountry users with how wide the fracture can travel across slopes. This layer will be slow to gain strength and requires careful terrain selection.
A less reactive layer of surface hoar or facets buried in early January can be found down 100-160 cm.
The mid/lower snowpack is generally well settled and strong in most areas.
