The wind effect from the last storm seems to be highly variable. 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
A fairly benign weather pattern is setting up for the forecast period. Light flurries are expected for Tuesday, but snowfall amounts shouldn't exceed 5cm. Isolated flurries with occasional sunny breaks are forecast for Wedesday and Thursday. Ridgetop winds are forecast to remain mainly light for all 3 days while alpine temperatures should hover between -12 and -15.
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 concern for a few days.
Snowpack Summary
Up to about 60cm of new snow fell over the weekend in the deeper snowpack parts of the region. Strong southwest winds redistributed much of this snow into much deeper wind slabs in exposed lee features in the alpine and at treeline. On sheltered lower elevation slopes I expect deep powder and really good riding.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 less likely. 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.