Regions
Kootenay Boundary.
New snow combined with sustained winds will keep our wind slab problem alive and well. Even if the rating is still Moderate, stability will be decreasing as new snow piles up.
Confidence
Moderate - Timing of incoming weather systems is uncertain on Sunday
Weather Forecast
Sunday: Flurries with 5-10cm of new snow arriving late in the day. Winds light to moderate from the southwest. Alpine temperatures around -5.Monday: Cloudy with scattered flurries and 4-7 cm of new snow. Winds light gusting to strong from the southwest. Freezing level to 900 metres with alpine temperatures of -4.Tuesday: A mix of sun and cloud with a trace of new snow. Winds light to moderate from the northwest. Freezing level to valley bottom with alpine temperatures of -8.
Avalanche Summary
A Size 1 wind slab avalanche was triggered by a skier in the Valhalla range on Thursday. The slide had a crown depth of approximately 30 cm and ran on a steep north aspect above 2000 metres in elevation. This serves as a good reminder that the wind slab problem hasn't disappeared yet and that it can be found on north aspects too. No new natural avalanches were reported today, but you can expect our new snow to sluff easily in steep terrain.
Snowpack Summary
Approximately 5 cm of new snow fell over Thursday night, covering facets and surface hoar which formed throughout the region during cold, dry weather earlier this week. On steep solar (south) aspects, a breakable sun crust may exist below the new snow. Recent cold temperatures have been promoting faceting, especially in the upper snowpack. The last snow we received (30-60 cm) was exposed to east through northerly winds during the cold clear period. While many areas saw "reverse loading" of the storm snow into wind slabs on south to west aspects, local wind patterns have seen slabs form on a wide range of aspects. Snowpack testing of various wind slabs continues to yield moderate to hard results with sudden fracture character. Below the wind slabs and storm snow, the weak layer buried on Boxing Day appears to have formed a good bond to the snow above. 50-70 cm below the surface we have another weak layer buried on December 18. This layer appears to be well bonded in most parts of the region, giving moderate results in snowpack tests, but not expected to be reactive to skier loads.
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.