For more information about the early December surface hoar problem, check out the forecaster blog.
Confidence
Fair - Due to variable snopack conditions
Weather Forecast
Monday: Expect mixed skies with a chance of flurries building later in the day. West winds with temperatures reaching -7. Tuesday &Wednesday: We should see a lull in the precip in the morning and then light flurries through the afternoon, evening and into Wednesday. Freezing levels will slowly rise from 1000-2000m under continued westerly winds.
Avalanche Summary
No new avalanches
Snowpack Summary
There is about 25-35cm of recent storm snow sitting over the December 12 interface of surface hoar and facets. This new snow has been deposited into soft slabs on lee features in open terrain by the consistent winds. The interface between the new snow and older surfaces is surface hoar and/or facets from early December. This layer is gaining strength, but still remains within the threshold of human triggering where there is sufficient load/slab properties. Check out the forecaster blog for more information on this layer and how to manage it. Lower in the snowpack, the mid-layers are well-consolidated and strong. Near the base of the snowpack there are a few layers that have the potential to trigger with very heavy loads or from shallow spots. These include a surface hoar layer from early November, a crust/facet combo from October and the interface on steep glaciated terrain with snow that did not melt over the summer.
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.