North Columbia

Keep seeking out soft, unconsolidated snow. Slab formation remains the critical factor for avalanche danger under present conditions. Plan on more conservative terrain selection at mid-elevations.

High -

Tuesday: Mainly cloudy. Light southwest winds. Alpine temperatures around -17.Wednesday: Cloudy with isolated flurries a trace of new snow, increasing overnight. Light southwest winds. Alpine temperatures around -16.Thursday: Mainly cloudy with isolated flurries and a trace of new snow. Light southwest winds, gusting to moderate. Alpine temperatures around -14.

Sunday's reports show continued observations of wind slabs releasing to Size 1 with skier traffic and ski cutting, primarily on south aspects around exposed terrain features in the alpine. One naturally triggered Size 1.5 was also observed on Sunday. Skier traffic has also been producing small dry loose sluffs from steep, sheltered terrain. A report from Friday showed one skier-triggered Size 2 persistent slab avalanche from a steep, rocky feature on a west aspect at 2100m in the Monashees. The late November crust was indicated as its failure plane. Persistent slab avalanche danger can be expected to persist in areas where last week's storm snow consolidates into a slab above the December 15 interface. In areas where the storm snow has not yet consolidated into a slab, expect continued potential for triggering loose dry avalanches in steep terrain.

Last week's storm brought 40-60cm of new snow to the region. Shifting winds (most recently from the northwest) have since redistributed this storm snow into wind slabs on a variety of aspects at higher elevations while cold temperatures have inhibited slab formation elsewhere. The storm snow lies over a wide variety of old surfaces, including large surface hoar (weak, feather-like crystals), hard crusts formed by sun or wind, and sugary facets. The bond at this old snow interface is of critical importance in areas where the overlying snow has consolidated into a slab. The most concerning areas are those that saw pronounced surface hoar development before the storm, particularly in sheltered openings at and below treeline. Recent snowpack tests show wide ranging reactivity at this interface but suggest that it may be most reactive on northerly aspects.A crust which was formed by rain in late November is another major feature in the snowpack and is down approximately 80-110cm at treeline elevations. Recent snowpack tests as well as an avalanche report from the North Monashees suggest it may be coaxed into reacting in steep, variably loaded terrain features.