South Columbia

Steady is the trend. Cold temperatures mean that persistent slab problems will be slow to heal. Stay watchful for signs of wind effect and slab formation at lower elevations.

High -

Wednesday: Mainly cloudy with isolated flurries and a 1-3 cm of new snow. Light southwest winds. Alpine high temperatures of -15.Thursday: Cloudy with flurries bringing 4-8 cm of new snow, increasing overnight. Light west winds. Alpine high temperatures of -10.Friday: Cloudy with flurries bringing 5-10 cm of new snow, increasing overnight. Light east winds. Alpine high temperatures of -12

Reports from Monday include observations of a recent Size 2 persistent slab release on a north aspect at 1800 metres, just northeast of Nakusp. Sunday's reports included observations of several older Size 1-1.5 natural wind slab releases, mainly on south aspects in the alpine. One report showed a skier-triggered Size 1 persistent slab releasing from a north aspect at 2200 metres. Reports from previous days include several more observations of wind slab releases from Size 1-2. Recent observations of persistent slab releases have been more limited, with similar size ranges but generally lower elevation ranges and more focused to north aspects. Persistent slab avalanche danger remains an ongoing concern in areas where last week's storm snow consolidates into a slab above the December 15 interface. In areas where new snow has not yet consolidated into a slab, expect continued potential for triggering loose dry avalanches in steep terrain.

Last week's storm brought 50-80 cm of new snow to the region. Predominantly north winds have since redistributed this storm snow into wind slabs on a range of aspects at higher elevations while cold temperatures have inhibited slab formation elsewhere. Cold has also worked to decrease cohesion and reactivity in older wind slabs. The storm snow lies over a variety of old surfaces, including large surface hoar (weak, feather-like crystals), 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, such as sheltered areas 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 formed by rain in late November is another major feature in the snowpack, found approximately 90-120cm deep at tree line elevations. Recent evidence from adjacent regions suggests it may be reactive in steep, variably loaded terrain features in the alpine.