New snow with moderate to strong winds on Saturday will continue to add to the reactive storm slabs at higher elevations. Be alert to conditions that change with elevation and use extra caution in wind exposed terrain.
The early December crust can be found down 90 to 200 cm below the surface, with weak, sugary crystals (facets) on top of it. The likelihood of triggering an avalanche on this layer is decreasing but still remains a concern for avalanches stepping down. We are now in a low probability/high consequence scenario with this layer.
Reactive storm slabs should be expected where the snow surface remains dry and crust-free at higher elevations. They will be most reactive in wind loaded terrain.
A relatively weak system is expected to reach the region early Saturday morning bringing light snowfall for Saturday. A ridge of high pressure is expected to establish by Saturday evening which should bring dry conditions for most of Sunday before the next system arrives Sunday evening.
Friday night: Mainly cloudy, light to moderate SW wind, freezing levels around 800-1000 m.
Saturday: Snowfall 10-20 cm, moderate to strong SW wind, freezing levels reaching around 1200-1400 m.
Sunday: A mix of sun and cloud in the morning, cloudy in the afternoon, light variable wind, freezing levels reaching around 800-1000 m.
Sunday night: Snowfall 15-20 cm, moderate to strong SW wind, freezing levels around 800 m.
Monday: Snowfall 10-15 cm, moderate SW wind, freezing levels reaching around 1200 m.
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 from the east of the region 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 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. Just south of the region, a size 3 cornice-triggered persistent slab avalanche was reported on a NE-E aspect at 2300 m failing on the same interface down 70-100 cm.
A thin new surface crust is being reported well into alpine elevations in the Monashees but does not seem to extend as high or be as prominent in the Selkirks. In many areas, this crust is reported to be sitting on moist or wet snow so the crust will likely get thicker as this snow refreezes. Below the new crust and at higher elevations, 20-50 cm of recent storm snow 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 Thursday 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.
