Avalanche Forecast

High -

Tuesday: A mix of sun and cloud. Light southwest winds. Alpine temperatures of -15.Wednesday: Mainly cloudy with isolated flurries and a trace of new snow, increasing overnight. Light southwest winds. Alpine temperatures around -14.Thursday: Cloudy with flurries bringing 5-10 cm of new snow. Light to moderate southwest winds. Alpine temperatures around -9.

Reports from Sunday 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. 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 can be expected to persist in areas where our recent 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. Recent shifting winds (primarily from the north) 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, 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 which was formed by rain in late November is another major feature in the snowpack, found approximately 90-120cm deep at tree line 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.