Avalanche Forecast

A ridge of high pressure brings some clearing before the next system arrives on Sunday afternoon bringing active weather for Monday. 

Saturday night: Mostly cloudy, light variable wind, freezing levels dropping to near valley bottom. 

Sunday: Mostly cloudy in the morning with sunny breaks, snowfall in the afternoon 5-10 cm, winds becoming moderate SW, freezing levels reaching around 1000 m.

Sunday night: Snowfall 10-20 cm, moderate SW wind, freezing levels around 600 m.

Monday: Snowfall 10-15 cm, moderate SW wind, freezing levels reaching around 1400 m.

Tuesday: Mainly sunny, light variable wind, treeline high around -6 °C. 

An early report from Saturday includes another persistent slab avalanche failing on the early December layer on a SE aspect at treeline in the southeast part of the region. 

On Friday, natural activity was limited to a natural size 3 storm slab failing from a steep rocky slope at 1700 m in the southeast of the region and two size 1 storm slabs on E-SE aspects at 1900-2100 m in the southwest of the region. Explosives triggered two size 2 cornice releases and several small storm slab avalanches. With better visibility, many operations were continuing to report evidence from the natural cycle on Wednesday/Thursday with numerous very large avalanches occurring in the storm snow. There was also another avalanche reported in the Selkirks which had stepped down to the early-December layer down 80-100 cm during the storm. 

On Thursday, a variety of natural and human triggered storm slab avalanches up to size 3.5 were observed throughout the region on all aspects at higher elevations. These were typically 20-40 cm thick but up to 100 cm in wind loaded areas. At lower elevations, natural loose wet activity was being reported. One natural size 3.5 persistent slab avalanche was reported in the Selkirks on a NE aspect at treeline failing on the early December interface down 150 cm. 

On Wednesday, a natural storm slab avalanche cycle up to size 3.5 occurred at higher elevations. In addition these storm slab avalanches, two persistent slab avalanches were observed failing on the early December layer, one in the Monshees and one in the Selkirks. One was reported on an E aspect failing down 130 cm and the other was also on an E aspect at around 1800 m failing down 110 cm.

One or two thin new crusts may be found in the upper snowpack which are now buried by 5-10 cm of new snow. The crust appears to be most prominent in the Monashees where it extends well into alpine elevations and possibly all the way to the mountain tops. In the Selkirks, the crust seems less developed and only extends to around 1700-1800 m. In addition to the new crust, a new layer of surface hoar has been reported and is now likely buried under the most recent snowfall. Below the crust and at higher elevations, 25-50 cm of storm snow from the past week is settling rapidly with the mild temperatures. This recent storm snow overlies the January 10 interface which may include weak facets and/or surface hoar. Another layer of facets from early January can be found down 50-90 cm.

The early December crust/facet interface is now typically down 80-140 cm, but as deep as 200 cm in wind loaded terrain. It consists of faceted grains above a bulletproof crust formed by the Atmospheric River rain event at the end of November. There has been avalanche activity on this layer as recently as recently as Friday in the region. Heavy triggers like natural cornice falls and storm slab avalanches may still have potential to step down to this layer resulting in very large avalanches. 

• Choose conservative terrain and watch for clues of instability.
• Avoid freshly wind loaded terrain features.
• Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.