Extensive wind effect has likely occurred at higher elevations. The best (and safest) riding may be found on sheltered slopes at treeline and below.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Light flurries and a mix of sun and cloud are expected for all 3 days of the forecast period. Moderate southwest ridgetop winds forecast for Monday and Tuesday will ease to light and westerly by Wednesday. The freezing level should sit at valley bottom for the foreseeable future. For a more detail weather discussion, please check-out our Mountain Weather Forecast at: avalanche.ca/weather.
Avalanche Summary
On Saturday there was evidence of 2 size 1.5 natural persistent slab avalanches. They failed between 1000 and 1100m, ran for about 100m and were up to 80cm deep. The early December surface hoar interface was the likely culprit in these events I'm sure there has also been a widespread round of natural wind slab activity in response to new snow and wind on Saturday night and Sunday. As the stormy weather eases, I'd expect natural wind slab activity to taper-off; however, human triggering will likely remain a real concern for a few days.
Snowpack Summary
On Sunday morning there was up to 30cm of fresh snow bringing the 48 hour total to about 50cm in the deeper snowpack parts of the region. Strong southwest winds have redistributed much of this snow into much deeper wind slabs in exposed lee features in the alpine and at treeline. Between 80 and 150cm below the surface you'll likely find a weak layer of well-developed surface hoar which was buried in early December. This layer is most widespread and reactive at lower elevations (between 1100m and 1800m.) Snow pit tests suggest that human triggering of this interface has become unlikely. That said, if it does fail the overlying slab is stiff enough to propagate over a wide distance. Below this layer, the snowpack is thought to be generally strong and well-settled.
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.