Regions
Kootenay Boundary.
Persistent slab problems are not obvious and tricky to manage. This problem may be found in unsuspecting locations at treeline and below and can catch you by surprise. Even a small avalanche in the trees can be consequential.
Confidence
High - The weather pattern is stable
Weather Forecast
The arctic ridge will continue to bring cold, dry air and northerly winds to the Kootenay Boundary tomorrow. Thursday will see a slight change when the low slides south bringing cloudy skies and some precipitation. Wednesday: Sunny with some cloudy periods. Treeline temperatures near -13 with light ridgetop winds from the North.Thursday: Cloudy with sunny periods. Treeline temperatures near -10 with light ridgetop winds from the North and freezing levels valley bottom.Friday: Cloudy with isolated flurries. Treeline temperatures near -10 with light ridgetop winds from the East.
Avalanche Summary
On Monday, reports indicated that the recent storm snow is reactive to human triggers up to size 2 on northerly aspects around 2100 m. The storm slabs were reportedly failing on most previous surface hoar interface down 20-30 cm which was buried February 1st. Several loose dry avalanches up to size 2 were also reported.
Snowpack Summary
10-30 cm of new snow falling late last week now sits on variety of snow surfaces, including buried wind crust on westerly aspects, crusts on southerly aspects to mountain top and weak feathery surface hoar in sheltered areas at treeline and below. In some places this surface hoar is reported to be sitting on a crust and has been reactive to light loads like people.Digging deeper 40-80 cm below the snow surface, expect to find another crust on south aspects and another layer of predominant feathery surface hoar crystals in sheltered and shaded areas. This deeper layer of surface hoar may be most reactive at treeline elevations on shady aspects. The remainder of the snowpack is generally well-settled and strong.
Problems
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.
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.