New snow and extreme ridgetop winds will keep the Avalanche Danger elevated over the next few days.
Confidence
Moderate - Intensity of incoming weather systems is uncertain on Sunday
Weather Forecast
Between 10 and 20cm of new snow and strong to extreme southwest ridgetop winds are expected on Sunday. Continued light flurries and moderate southwest winds will persist for Monday and Tuesday. Freezing levels should sit at valley bottom for all 3 days. For a more detailed weather overview, check out our Mountain Weather Forecast at avalanche.ca/weather.
Avalanche Summary
There have been no recent reports of avalanche activity. This may speak more to a lack of observations rather than actual conditions. Wind and new snow will likely be the driver for wind slab avalanche activity over the next few days.
Snowpack Summary
Steady snowfall over the past few days and moderate southwest winds have formed fresh 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. This layer is most widespread and reactive at lower elevations (between 1400m and 1800m.) Snow pit tests suggest that human triggering of this interface is still possible, although 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.