Regions
Kootenay Boundary.
Confidence
Fair - Intensity of incoming weather is uncertain
Weather Forecast
Thursday: should stay cold and dry, although not quite as cold as it has been (-11C at treeline expected). Winds will increase slightly but should stay in the moderate range, and will shift back around to the west. Friday: a storm is approaching, which will hit the region late in the day. Anticipated amounts are 5-10 cm new snow with temperatures rising to around -6C. On Saturday, a further 10-15 cm new snow is anticipated, with freezing levels possibly rising briefly to 1500 m.
Avalanche Summary
Ski cutting produced size 1 loose and occasional soft slab avalanches on Wednesday with minimal propagation. Widespread sluffing to size 1 was noted on Tuesday and Wednesday in the new snow on steep terrain.
Snowpack Summary
The storm on Monday night/Tuesday added 15 to 40 cm very low density new snow, bring average treeline snow depths to around 200 cm. Cold temperatures have kept the snow light and cohesionless in most areas, despite recent moderate winds that have been blowing snow around a little. A crust now lies buried around 25-45 cm below the snow surface at elevations below 1900 m. Some areas reported this crust had a layer of surface hoar on it when it was buried. It appears at this time as though the snow has not yet settled enough to produce much slab avalanche activity on this layer yet. However, when the upper slab does become sufficiently cohesive, more dangerous avalanche conditions will start to set up. There is a blog posting on the Forecaster Blog (link on the sidebar on the left) that discusses this issue in more depth. The mid-December surface hoar/facet persistent weakness, now down 70-120 cm, remains a concern with heavy triggers in thin slab areas.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.