Regions
Kootenay Boundary.
Saturday’s danger ratings are based on intense sunshine and warming affecting the upper snowpack.
Confidence
Fair - Timing or intensity of solar radiation is uncertain on Saturday
Weather Forecast
Saturday: Light W winds. Alpine temperature near +3. Sunny skies, with valley cloud. No snow.Sunday: Moderate SW wind. Alpine temperature near -4. Light snow is possible.Monday: Light SW wind. Alpine temperature near -5. Light snow.
Avalanche Summary
Size 1 to 2 loose dry avalanches have been failing with natural and human triggers in steep terrain. Human-triggered slabs (size 1 to 2) have also been failing on the Jan 23 interface. In many cases, these events have been on wind-loaded aspects.
Snowpack Summary
Recent NW winds have redistributed 15-40 cm of recent snow into soft or hard slabs on lee slopes in the alpine and at treeline. A weak interface buried on Jan 23 seems to be becoming more reactive as the slab above settles and becomes more cohesive. Deeper, about 50-60cm down, a weak interface buried in early January exhibits moderate to hard, sudden results in snowpack tests. The snowpack below this is generally well bonded. Forecast warming may increase the likelihood of triggering a persistent slab.
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.