Regions
Kootenay Boundary.
Confidence
Poor - Track of incoming weather is uncertain on Wednesday
Weather Forecast
Tuesday: Continued isolated flurries with freezing levels in valley bottoms and strong westerly alpine winds. There is high uncertainty with the weather for Wednesday and Thursday. Some forecast models are calling for moderate snowfall while others are calling for almost none. It all has to do with track of a frontal system that's primarily heading south of the region. If heavy loading from snow or wind does occur, then expect avalanche danger to increase.
Avalanche Summary
Reports from yesterday include isolated Size 1 human triggered wind slab avalanche on a east-northeast facing alpine slope near the ridgecrest, generally sluggish and slow moving. Low density storm snow is sluffing readily in steep terrain with a natural cycle overnight Saturday. In some cases they're entraining considerable mass and reaching up to Size 2.
Snowpack Summary
Snow flurries have maintained a fresh snow supply for wind slab development and cornice growth, but remains fluffy and cohesionless in most sheltered areas. Surface hoar and/or faceted snow, with an associated crust making it especially touchy on sun-exposed slopes, was buried last week and is now down 15-25cm. Below that a thin melt/freeze crust buried early-January can be found as high as 1900m, and some areas are reporting surface hoar . The mid-December surface hoar/facet persistent weakness, now down 50-120cm, remains a concern with heavy triggers in thin slab areas. Basal facets remain concern in shallow snowpack areas especially with heavy triggers in thin spots, and weaknesses in the slab above create the potential for step-down avalanches.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.