Avalanche Forecast

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Heaviest snowfall amounts are forecast for Kootenay Pass, where 40+ cm are forecast to fall per 12 hour period overnight Thursday and during the day Friday.

Thursday night: Snowfall 15-30 cm for most areas, upwards of 40 cm at Kootenay Pass. Strong SW wind. Treeline temperature around -8 °C. 

Friday: Snowfall 15-30 cm in most areas, upwards of 40 cm at Kootenay Pass. Strong SW wind. Treeline high around -3 °C. 

Saturday: Mix of sun and cloud. Moderate to strong SW wind. Treeline high around -6 °C. 

Sunday: Mix of sun and cloud. Moderate SW wind. Treeline high around -3 °C. 

On Wednesday, wind slabs were reactive to explosives up to size 2 in the west of the region. On Monday and Tuesday, storm slab avalanches were reactive naturally and to skier and explosive triggers, up to size 2.

There has been an alarming pattern of large, persistent slab avalanches being consistently reported over the past two weeks. Almost all of these avalanches ran on the early December weak layer. Deeply buried persistent problems like these don't go away overnight, and it remains a serious concern. Additional loading by the weight of new snow will further stress this weakness and may result in a resurgence of reactivity.

• On Tuesday, explosive control work near Rossland produced a size 2.5 persistent slab avalanche on a layer of surface hoar from late December. 
• On Monday in the neighboring South Columbia region, a natural size 2.5 persistent slab avalanche was reported on a NE aspect at 2200 m failing 80 cm deep on the early December layer.
• A few notables from last week feature in our latest blog Photos of recent persistent slab avalanches in the southern interior. 

30-60 cm of new snow is forecast to fall by the end of Friday amid strong wind. As temperatures climb, this warmer, denser new snow will likely form a slab over previous lower density snow. An accumulated total of 70-100 cm of new and recent snow now sits over variable and potentially weak snow surfaces including widespread facets, wind affected snow, and/or surface hoar up to 5 mm in sheltered areas, which may make for a weak bond at this interface.

The early December crust/facet layer has been responsible for sporadic but very large persistent slab avalanches over the past two weeks. The crust is now buried over 1 m deep except in thin, wind affected areas near ridgetops where nearly all of the recent avalanches have been triggered. We have uncertainty around whether new snow loads will cause this layer to fail naturally in the short term, or to help it heal in the longer term.

• Storm slab size and sensitivity to triggering will likely increase through the day.
• Storm slabs in motion may step down to deeper layers resulting in large avalanches.
• Avoid exposure to overhead avalanche terrain, avalanches may run surprisingly far.
• Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.