Kootenay Boundary

Heavy snowfall and extreme winds will bring the Avalanche Danger to HIGH. Very conservative terrain selection is critical.

Good

A frontal wave will track over the South Coast and track eastward just south of the boarder. This pattern is forecast to bring heavy snowfall to the region (up to 35cm) by Monday morning. Moderate snowfall is forecast to continue throughout Monday and into Tuesday morning. By Tuesday afternoon, a drying trend is expected to develop and carry into Wednesday. Remnant arctic air will keep freezing levels at valley bottom on Sunday night. However, freezing levels are expected to rise somewhat (as high as 1000m in the south of the region) by Monday night as the arctic air retreats and gives way to the warmer southwest flow. On Wednesday, an inversion is likely with above-freezing alpine temperatures. Ridgetop winds are expected to remain mainly westerly for the forecast period. They should hit extreme values on Sunday night and Monday morning, and then remain mainly moderate to strong for the rest of the forecast period.

In general, persistent slab avalanches to size 2 continue to occur in the Kootenay Boundary region. On Sunday, skiers accidentally triggered size 1.5 slabs around treeline in the Selkirks and the Monashees. Both avalanches failed on the mid-December layers.With the storm forecast for Sunday night, I would expect fairly widespread storm slab activity with many avalanches stepping down to the mid-December crust/ surface hoar interface.

With the storm forecast for Sunday night, expect deep and reactive storm slabs to develop. The new snow will overlie a variety of old surfaces which include heavily wind-affected surfaces in exposed locations, and faceted powder and buried surface hoar in sheltered terrain. Up to 80 cm below the surface, you'll likely find a touchy weak layer of surface hoar sitting on a thick rain crust. This widespread persistent weakness continues to be the primary layer of concern for the region. With forecast storm loading, I expect this layer to become even more reactive, with the potential for large and destructive avalanches. At the base of the snowpack, a crust/facet combo appears to have gone dormant for the time being.