Avalanche Forecast

Brrrrrr! Cold and dry conditions persist under arctic air

Wednesday night: Mostly clear, light northeast ridgetop wind, alpine temperature -27 C.

Thursday: Sunny, light to moderate northeast wind, alpine high temperature -27 C.

Friday: Sunny, light to moderate northeast wind, alpine high temperature -20 C.

Saturday: Increasing cloud, moderate east wind, alpine high temperature -18 C. 

A very large (size 3) natural wind slab avalanche was reported on Sunday near Valemount. It released on a northeast aspect above 2500 m and broke 100 cm deep. There was also a second-hand report of a large (size 2) wind slab on a north aspect at 1800 m near Barkerville. This avalanche was thought to have been initiated by a machine-triggered cornice fall on Saturday.

Over the past week, there have been reports from Chappell, White River, and Allen Creek of avalanches releasing on a persistent weak layer of surface hoar. Although the likelihood of triggering these avalanches is decreasing, this weak layer warrants assessment in open, sheltered slopes at treeline where this layer is likely pronounced and preserved.

Small (size 1-1.5) loose dry avalanches in unconsolidated snow have been reported in steep terrain.

Up to 25 cm of low density snow at the end of last week has combined with periods of moderate northwest winds to create wind slabs which may be possible to human trigger 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, there is uncertainty as to how much direct sun on Tuesday might warm steep slopes midday given the frigid temperatures.

40-70 cm of snow from the past week is settling over a reactive weak layer of surface hoar. Reactivity on this layer has primarily been observed at treeline and in "treeline-like" features that are below treeline. Snowpack tests results continue to show the potential for propagation on this layer, like this MIN report from near Barkerville on Sunday. 

A second weak of layer of surface hoar from mid January is down around 70-110 cm and is most prevalent in sheltered, open slopes at treeline and below. 

Deep persistent weak layers can still be found in the lower snowpack. These weak layers are most likely to be triggered from rocky areas with a shallow or thin to thick snowpack.

• Carefully evaluate steep lines for wind slabs.
• Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
• Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.