Skiing is still quite good out there if you can find places where others haven't been. Keep an eye out for the Dec4th layer and the slabs sitting over top of it. Slabs that are stiff should be treated with more suspicion and caution. PJ
Confidence
Moderate - Forecast snowfall amounts are uncertain on Friday
Weather Forecast
Light northwesterly flow will continue tomorrow with cloud, a few sunny periods and no precip. Freezing levels will remain in valley bottom. The upper flow will shift to the west with moderate to strong winds and some light snowfall (10-15cm's) for Friday along the divide.
Avalanche Summary
Very little to no avalanche activity this past week either naturally, explosive or human triggered.
Snowpack Summary
Light winds have prevailed this week and so very little wind effect. Colder temperatures are creating some recrystallization of the surface snow into facets and some smaller 2-3mm surface hoar has been noted at treeline elevations the past couple of days. Keep this in mind when more snow arrives accompanied by wind. The main issue with this snowpack at the moment is the Dec 4rd interface which is approximately 30-45 cms below the surface depending on elevation. Surface hoar and facets exist at this interface on the the north aspects (especially below 2300 meters) and temperature crusts and wind impacted surfaces everywhere else. The storm slab that sits on top of this interface is quite soft for the most part, so very little tension to initiate at the moment. In the higher alpine elevations, more snow and wind effect has been observed and these are the places where the Dec 4th layer will be more sensitive to triggering.
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.