Avalanche Forecast

A weak ridge of high pressure will strengthen over the Interior and generate strong outflow winds along with residual flurries for the weekend. A warm front is expected to invade the region Monday night, with widespread snow and significantly warmer temperatures. 

SATURDAY NIGHT: Overcast. 0-8 cm of snow expected. Light southwest winds trending to strong at higher elevations. Treeline high around -10 C. 

SUNDAY: Overcast. Possible trace of snow expected. Light southwest wind trending to strong at higher elevations. Treeline high around -7 C. Possible temperature inversion setting up.

MONDAY: Mostly clear, with increasing cloud through the day. Possible trace of snow expected. Moderate southeast winds trending to strong southwest at higher elevations. Freezing level rising to around 500 m. A temperature inversion could mean that the temperature above 2000 m will be above -5 C.

TUESDAY: Mostly cloudy. 2-10 cm of snow expected. Moderate to strong southwest wind trending to extreme at higher elevations. Possibly above 100 km/h. Freezing level rising to around 800 m.

On Friday and overnight into Saturday, numerous natural and rider triggered storm slab avalanches up to size 3 were reported by professional operations in the region. Avalanche control with explosives produced size 1.5 to 3.5 avalanches, mostly in the storm snow.

A very large storm slab avalanche (size 3) ran naturally in Mount Revelstoke National Park on Friday afternoon. Up to 3 m of snow buried the highway. This avalanche path rarely affects the road (only once every 5 or 10 years). The avalanche appears to have started as a storm slab, and stepped down to a deeper, persistent layer.

Widespread loose dry avalanches were observed on unsupported features at treeline and below during the storm. Storm snow was very reactive to riders, as they were able to easily trigger soft slabs avalanches up to size 1.5 within the new snow. 

Although the persistent Dec crust/facets layer has recently been more active south and east of this region (details and photos here) it remains a concern in the Columbias as well. On Friday, two naturally triggered size 2 avalanches on this layer were reported near Monashee Provincial Park. They both started as windslab avalanches, and stepped down to this deeper, persistent layer in a thin, rocky area. 

The region received 35 to 50 cm low-density snow and consistent 50 km/h southerly wind since the start of the storm Thursday. This new snow fell on a variety of surfaces, thin sun crust on solar aspects, isolated surface hoar at treeline on sheltered slopes, fresh wind slabs in lee alpine features at treeline and above or even previous storm snow (20-50 cm) from the last weekend's storm.

We're actively monitoring the early December crust. In some places, it's scoured and on the surface, while in wind-loaded terrain features it can be found as deep as 150 cm below the surface. It consists of faceted grains above a bulletproof crust formed by the Atmospheric Rivers of early December. Avalanches failing on this interface have the potential to be very large. 

• Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
• Keep in mind that human triggering potential persists as natural avalanching tapers off.
• Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.
• Be carefull with sluffing in steep terrain, especially above cliffs and terrain traps.
• Storm slabs in motion may step down to deeper layers resulting in large avalanches.