Avalanche Forecast

Saturday night: Mostly clear, light east wind, alpine high temperature -20 C, freezing level at valley bottom.

Sunday: Sunny, light northeast wind, alpine high temperature -14 C, freezing level at 800 m. 

Monday: Sunny, light north wind, alpine high temperature -8 C, freezing level at 1300 m.

Tuesday: Mostly sunny, light northerly wind, alpine high temperature -5 C, freezing level 1700 m.

Numerous wind slab and storm slab avalanches up to size 3 were triggered naturally and by humans during the storm mid week and the number of avalanche reports has decreased since then. Many avalanches released on the old snow surface which consists of a weak surface hoar layer and a sun crust on steep solar aspects. Reports of avalanches releasing on this layer continued into Thursday. Some of these avalanches stepped down to the persistent weak surface hoar layer from February 22 and resulted in large avalanches up to size 3. 

Reports of large (size 2-3) human, remotely and explosive-triggered avalanches releasing on the February 22 surface hoar layer continued over the past week from operators region-wide. This layer continues to surprise people with remote-triggered activity, wide propagation, and a false sense of stability from unreactive ski cuts or from multiple people moving through the terrain before an avalanche releases (see this Instagram report as a good example). Observations have extended to all aspects and elevations, but north to east aspects near treeline have been a hot-spot for reactivity. Avalanches have also occurred at unusually high elevations for surface hoar, with several cases of wind slabs stepping down in the alpine. While the number of reported avalanches has decreased, the size has increased, with more of the activity releasing size 2+.

Moderate northeast wind has redistributed the snow and formed wind slabs in exposed terrain. The recent snow may sit on a surface hoar layer and a sun crust on steep solar aspects. This layer is responsible for many avalanche releases and might develop into a persistent weak layer. 

A widespread weak layer of surface hoar is buried 60-120 cm deep. On solar aspects, this layer may sit over a crust. This persistent slab problem has transitioned into a low probability/high consequence scenario. If triggered, avalanches will be large and getting caught could have serious consequences. Managing this problem requires a patient and diligent mindset, implemented by avoiding suspect slopes and maintaining conservative terrain margins. This persistent weak layer will likely pose the threat of a low probability/high consequence avalanche until there is a substantial change in the snowpack. Read more about surface hoar on our forecaster blog.

• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.
• Be aware of the potential for large avalanches due to the presence of buried surface hoar.
• Minimize exposure to steep, sun exposed slopes, especially when the solar radiation is strong.