Avalanche Forecast

Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system.

Monday night: Cloudy, 10-20 cm of snow, light southwest wind, alpine temperature -6 C.

Tuesday: Cloudy, 20-30 cm of snow, moderate southwest wind, temperatures warming throughout the day with a high of -2 C in the late afternoon, freezing level rising to 1000 m.

Wednesday: Cloudy, 20-30 cm of snow overnight, moderate southwest wind, alpine high temperature -3 C, freezing level dropping to valley bottom.

Thursday: Partly cloudy, light northwest wind, alpine high temperature -9 C. 

New snow and wind are expected to induce a natural avalanche cycle. More reactive storm slab avalanches have the potential to step down to multiple buried weak layers producing large and destructive avalanches. 

Over the weekend, there were reports of large (size 2-3) avalanches breaking on a layer of surface hoar from late or mid-December on a variety of aspects and elevations from natural, human, and explosive triggers. A few of these avalanches were triggered remotely (i.e. from a distance). Three notable persistent slab avalanches released naturally on east and northeast facing slopes above 2200 m in the southern part of the region on a crust/facet layer from late November buried 150 cm deep. These avalanches give clear evidence that the continual loading on this fundamentally weak snowpack structure remains a serious concern.

The incoming storm is forecast to bring 30-40 cm of snow to the region throughout the day on Tuesday with moderate southwest wind, forming a new storm slab problem that will need to be managed. Expect areas where the snow is being drifted by wind to more rapidly develop this storm slab problem.

There are multiple weak layers buried in the snowpack. A weak layer of feathery surface hoar is buried around 60 to 100 cm deep. Around 110 to 150 cm deep, another surface hoar layer may be found, and a facet/crust layer from late November lingers near the bottom of the snowpack. This fundamentally unstable snowpack structure remains a concern, as it is capable of producing large and destructive avalanches. It is possible that storm slab avalanches could step down to these deeper layers or that the layers could be triggered in areas where the snowpack is relatively thin.

• Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
• Watch for changing conditions today, storm slabs may become increasingly reactive.
• Storm slabs in motion may step down to deeper layers resulting in large avalanches.