Avalanche Forecast

Brrrrrr! Cold and dry conditions persist under arctic air

Wednesday night: Mostly clear, light northeast ridgetop wind, alpine temperature -26 C.

Thursday: Sunny, light northeast ridgetop wind, alpine high temperature -26 C. 

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

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

Several small to large (size 1-3) natural, human and machine triggered wind slab avalanches were reported over the last couple days. These avalanches released on northeast through east through south aspects above 2000 m and broke 10-30 cm deep. A few of these wind slabs were solar-triggered by large cornice falls.

Over the past week, avalanche activity failing on a widespread layer of surface hoar buried 60 cm deep has decreased. How quickly this layer will gain strength is uncertain. This persistent slab problem warrants assessment in open, sheltered slopes at treeline where it is likely pronounced and preserved. 

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

Up to 35 cm of low density snow over the weekend has combined with periods of moderate northwest winds to create wind slabs which may be possible to human trigger in specific 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 the direct sun will warm steep slopes midday given the frigid temperatures.  

60-100 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 Clemina on Monday and this MIN report from the Gorge on Tuesday. 

A less reactive layer of surface hoar or facets buried in early January can be found down 80-130 cm.

The mid/lower snowpack is generally well settled and strong. 

• 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.