Avalanche Forecast

Sunday night: Mostly cloudy, isolated convective flurries with a trace of accumulation, moderate northwest winds, alpine temperature -16 C.

Monday: Mostly clear, light northwest winds, alpine high temperature -11 C.

Tuesday: Increasing cloud, 5-10 cm of snow, moderate southwest winds with strong gusts, alpine high temperature -10 C.

Wednesday: Cloudy, 10-20 cm of snow, moderate southwest winds with strong gusts, alpine high temperature -7 C, freezing level rising to 900 m.

Throughout the storm, there have been reports of very large (size 3-3.5) natural avalanches releasing in the new snow on all aspects and mainly at treeline and alpine elevations. A large cornice fall was reported Sunday on a steep north facing slope at tree line. Cornices may act as triggers for large wind slab avalanches. Below tree line, wet loose avalanches were releasing naturally during the warm temperatures on Friday.

With continuous stormy weather over the past week, operators have reported three persistent slab avalanches that were both naturally and skier-remote triggered. These very large (size 2.5-4) avalanches were breaking 100-200 cm deep across a variety of aspects above 1900 m. Easier-to-trigger wind slab avalanches or cornice fall may have the potential to step-down to this layer.

There have been substantial changes to the snowpack over the past few days. 40-60 cm of snow fell during the weekend storm above 1700 m. Higher snow totals fell in the southeastern parts of the region. Strong winds originating from the southwest and shifting to the northwest have created a tricky loading pattern near and above tree line and have elevated concern for cornice triggers. These winds have drifted the snow into stiff slabs on leeward terrain features that remain prone to human triggering. Check out this MIN report for a helpful illustration of these conditions. 

During a warming event Saturday night, rain saturated snow surfaces up to around 1700 m that have since refrozen with cooling temperatures.

The mid and lower snowpack are generally well settled and strong, however there is a weak layer of surface hoar currently buried 70 to 150 cm deep. This layer has recently shown signs of instability in the region. New snow, rain, and warming have added considerable strain to this weak layer, and it may require more time to adjust to the recent load.

• Stay off recently wind loaded slopes until they have had a chance to stabilize.
• Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
• If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.