Regions
Banff Yoho Kootenay.
Although we are now in a period of moderate avalanche danger, pay attention to what the wind is doing. With strong winds, slabs can build up quickly and overload the weak surface hoar/facets. Dig into the snow before committing to a slope.
Weather Forecast
Strong W winds and above-normal temp's are the main factors for the next couple of days. Expect the winds in the alpine to be strong, redistributing any loose snow leftover from the last couple of days of wind.
Snowpack Summary
30 to 50cm of snow sit over the Jan 6th interface. In several locations in Kootenay and some areas near Sunshine, the Jan 6 interface is a well preserved surface hoar (3 to 5mm in size). Tests show easy sudden planar shears. It's worth digging down to it in a few locations to check if it's present. Alpine features have been blasted by recent wind.
Avalanche Summary
During the wind event over the past few days, several size 1.5 - 2 avalanches were noted in the alpine. One skier triggered a size 1.5 avalanche near sunshine in an open wind affected lee feature below treeline. May see continued sporadic small avalanches tomorrow with strong winds forecasted, although most of the snow has been moved already.
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.