Avalanche Forecast

The arctic grip continues. Temperature decrease over the week with light snowfall possible each day.

SATURDAY NIGHT: Up to 5cm overnight. Easterly winds. 

SUNDAY: Light snowfall over the day, up to 5cm expected. Light to moderate easterly winds. Alpine highs of -20.

MONDAY: Clearing skies with increasing westerly winds. Alpine high of -20.

TUESDAY: Partly cloudy with isolated flurries. Alpine high of -22. Light westerly winds. 

The heavy snowfall this week produced a natural slab cycle to size 3 throughout the region on Wednesday and Thursday. Human triggered slabs were also observed to size 1 in wind loaded features.

A notable size 1 remote wind slab was remotely triggered on a north aspect below treeline. Riders felt a settlement while in the runout, and this triggered the slab on a steep piece of terrain on an adjacent slope. While this avalanche was small, it does indicate the reactivity of the persistent weak layers in the lower snowpack and the potential for fractures to travel over a distance. This avalanche problem is challenging to forecast and is best managed by conservative terrain management. 

If head into the mountains, please submit your findings and photos through a Mountain Information Network report.

Up to 40cm of fresh storm snow has accumulated this week. In the alpine and exposed treeline elevations it has been redistributed into deeper deposits in wind loaded features by wind. In the southern parts of the region, southwest winds have been dominant. In the northern part, southwest winds came in with the snow and are now followed by a northerly blast, redistributing snow into unusual loading patterns. 

At lower elevations the settling storm snow may sit over a weak surface hoar layer, which is creating slabs that are reactive to human triggers. The surface hoar is most likely to be found on sheltered slopes at treeline and below.

The crust formed by the early December rain event sits 100-150cm deep and is found up to 2200m in the North Columbia's. In most terrain the snow above is well bonded to the crust. In areas where the crust is buried deeper than one meter, it has begun to decompose and shows limited reactivity.

However in some areas, weak faceted grains have been observed above - creating a weak interface that is still reactive to human triggers. This is most common at treeline elevations where the crust is thinner. 

• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
• Be aware of the potential for large avalanches due to the presence of a persistent slab.
• Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.