North Columbia

The persistent slab problem is best managed with patience and conservative terrain choices. Read more in the new forecaster blog here.

Moderate.

SUNDAY NIGHT: Isolated flurries with localized accumulations of 2-5 cm, light wind from the southwest, alpine temperatures drop to -8°c. MONDAY: Mostly cloudy with a few sunny breaks, light wind, alpine high temperatures around -6°c. TUESDAY: Mostly cloudy with a few sunny breaks, light wind, alpine high temperatures around -8°c. WEDNESDAY: Mostly cloudy, light wind, alpine high temperatures around -10°c.

On Saturday, a few large (size 3) avalanches were triggered by explosives on south-facing alpine slopes. The avalanches released on persistent weak layers 60-150 cm deep. Otherwise, natural and human triggered activity has started to tapered off. Over the past week, several notable persistent slab avalanches have been remotely triggered from skiers on adjacent slopes, particularly in the Selkirks and the northern tip of the Monashees near Valemount. The most recent occurred in the Selkirks on Friday, where a size 2.5 slab was remotely triggered on a south slope at 2200 m from low angle trees. The avalanche failed on a 120 cm deep surface hoar layer.

Strong wind from various directions has formed wind slabs in the alpine and around treeline. A week of stormy weather has deposited 80-120 cm of snow above a weak layer of facets (sugary snow), surface hoar (feathery crystals), and a sun crust (on south aspects) that formed during the dry spell in early December. This layer has been responsible for large persistent slab avalanches over the past week, particularly on northeast facing slopes above 1900 m and on south-facing slopes in the alpine. The potential exists for smaller avalanches to step down and trigger this layer, resulting in very large avalanches. Another weak layer from mid-November is now buried up to 150 cm, but has been less active recently. At the base of the snowpack is a crust that formed in late October. Concern for these layers has dwindled, but they may still be worth considering in places such as steep, rocky, alpine terrain.