Avalanche Forecast

Unsettled conditions are expected on Tuesday in the wake of the storm. Periods of light snow and periods of sun are both possible. 

Monday night: Snowfall 5-10 cm, moderate to strong SW wind, treeline temperature around -10 °C. 

Tuesday: A mix of sun and cloud with periods of flurries, light to moderate SW wind, treeline high around -10 °C. 

Wednesday: A mix of sun and cloud with a chance of flurries in the morning, light to moderate N wind, treeline high around -12 °C. 

Thursday: Snowfall 2-6 cm, moderate to strong SW wind, treeline high around -12 °C. 

Early reports from Monday include natural size 1 winds slabs and explosive triggered storm slabs up to size 2. This MIN report from the south of the region shows an example of the instability in the storm snow and good decision making. 

There has been consistent reports of persistent slab avalanches on reloaded bed surface crusts from the Invermere area over the past month. On Sunday, one of these events was reported on a N aspect in the alpine. On Thursday, a size 1 was triggered remotely by bootpacking on a thin northeast aspect in the alpine. Explosive control work on December 26th produced large avalanches (size 2) on the crust found 40-70 cm deep.

On Tuesday, recently formed slabs are expected to remain reactive to human triggering. These new slabs sit on a weak interface and may be very reactive, especially in wind loaded terrain. In the areas that received more than around 25 cm, the new slabs are expected to be widespread while in the areas with less new snow, the problem will likely be isolated to wind loaded areas. The persistent slab problem remains a serious concern and the weight of the new snow may increase the reactivity of these deeper layers. Smaller storm slab and wind slab avalanches also have the potential to step down to deeper layers resulting in very large avalanches. 

The new storm snow buried a variable snow surface which is likely weak and includes widespread facets, wind affected surfaces, and/or surface hoar up to 3 mm in sheltered areas. The new snowfall was accompanied by moderate to strong winds and new storm slabs are expected to be most reactive in wind loaded areas. 

The most notable layer of concern in the snowpack is a crust that was formed in early December and is now down 70-150 cm. Activity on this layer has been sporadic. It has generally been triggered on steep, rocky slopes, with a shallow or thin-to-thick snowpack. This layer has created a low likelihood, high consequence scenario which is best managed through conservative terrain choices and disciplined backcountry travel techniques.

A late October facet/crust layer sits at the bottom of the snowpack above 1900 m. 

• Continue to make conservative terrain choices while the storm snow settles and stabilizes.
• Be aware of the potential for large avalanches due to the presence of a persistent slab.
• Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.