Kootenay Boundary

The new storm will rapidly increase the avalanche danger. Some areas with heavy snowfall may reach High danger by Tuesday evening.

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Due to the remnants of the recent cold weather and the angle of the approaching storm, it looks like the freezing levels will remain at valley bottoms until early Wednesday. Expect strong southwest winds and a couple of cm of new snow overnight. On Tuesday the winds will reach extreme values from the southwest as the storm drops 10-20 cm of new snow. Expect another 15-30 cm by Wednesday morning combined with strong to extreme southwest winds and freezing levels rising up to about 1500 metres. Thursday should be slightly cooler with moderate southwest winds and 5-8 cm of snow.

Windslab and loose snow avalanches have been likely to be triggered in isolated terrain by the additional load of a skier or rider. Conditions are expected to change overnight as a new storm moves into the region and new storm slabs develop. I expect this will result in a direct action cycle of storm slab avalanches. As the load increases over the next few days we will be looking closely at recent persistent weak layers and discussing the likelihood of these layers failing under the new load of storm snow combined with wind and warm temperatures.

The new storm is arriving overnight and expected to intensify during the day. Expect new storm slabs to develop above existing weak layers described here. Recent cold and clear weather has promoted both faceting of surface snow as well as the growth of surface hoar that has been reported to be up to 15mm in size below treeline. A sun crust has also been reported forming on steep solar aspects. Below the surface, up to 20 cm of recent snow has been redistributed by moderate to strong winds from all directions, forming reactive wind slabs on a variety of aspects. The recent snow buried a plethora of old snow surfaces, including wind scoured surfaces and old wind slabs, widespread near surface faceting (sugary snow), surface hoar in sheltered locations, and/or a breakable sun crust on steep solar aspects. The mid-December surface hoar/ facet layer typically sits down 40-70 cm. This layer is still reactive to some snowpack tests in some areas but is currently considered to be dormant or inactive. However, once the snowpack starts to see a big change, like warming, the likelihood of triggering may increase.