Kootenay Boundary

Wind slabs remain the primary concern for Friday. In the mountains west of Trail and Castlegar, a spotty layer of surface hoar has recently been reactive and human triggering of this layer remains possible.

Moderate -

Another 5 cm of snowfall is expected Thursday overnight with strong southwest wind in the alpine shifting to moderate from the northwest. Lingering flurries are forecast for Friday morning with dry conditions and a mix of sun and cloud in the afternoon. Alpine wind is forecast to be light to moderate from the north and treeline temperatures are expected to around -10C. A mix of sun and cloud is expected on Saturday with moderate alpine wind from variable directions and treeline temperatures remaining around -10C. Around 5 cm of snowfall is currently forecast for Saturday night. Unsettled conditions are forecast for Sunday with the light snow in the morning and sunny breaks in the afternoon.

On Wednesday, a natural size 1 storm slab avalanche was reported on a north aspect at 2100 m which had a slab thickness of 20-40 cm. Skiers and explosives were also triggering storm slabs and wind slabs size 1-2 with typical slab thickness of 20-50 cm. In the mountains west of Trail and Castlegar, a ski cut produced a size 1 persistent slab avalanche on a south aspect at 2100 m. This failed on the mid-December surface hoar layer down 40cm. This is the third avalanche reported on this layer in the same area in the past week. On Tuesday, a skier triggered a size 1.5 slab on this layer on a northeast aspect at 2100 m with a thickness of 40-60 cm. On Monday, a skier triggered a slab on this layer on 40 degree slope on a northeast aspect. On Friday, wind slabs are expected to remain the main concern. Strong southwest winds over the last few days have built touchy wind slabs.  On Friday, winds are expected to switch direction and blow from the north which may result in some reverse loading. In the mountains west of Trail and Castlegar, extra caution is required in areas where surface hoar may be preserved.

30-60 cm of snow has accumulated since Monday. The new snow sits over a variable interface which may consist of wind scoured surfaces or old wind slabs in exposed terrain, surface hoar up to 5 mm in sheltered areas and/or a freezing rain crust. Recent test results suggest the layer is gaining strength but may still be reactive in isolated areas. In exposed terrain, strong southerly winds have redistributed the new snow and wind slabs exist in leeward terrain features. The mid-December interface is now down 40-100 cm. This layer appears to be well bonded in many parts of the region but has recently been reactive in the mountains west of Trail and Castlegar where the interface is down around 40 cm. It appears that preserved surface hoar is creating an isolated problems for this area and three skier trigger avalanches have released on this layer since Monday.