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Confidence
Fair - Intensity of incoming weather is uncertain on Saturday
Weather Forecast
The snow is expected to intensify Friday evening. The pacific system is angled a bit to the north of Revelstoke. The North Monashees and the Cariboos should see close to 30 cm by Saturday morning. The Selkirks and South Monashees will probably see closer to 20 cm. Further south should see lesser amounts. Strong winds 60 km/hr with gusts to 80 km/hr are forecast from the southwest on Friday night and Saturday. Some models are showing high freezing levels for Saturday, possibly up to 2000 metres. I think that it is more likely that the freezing level will reach to about 1600 metres in the southwestern ranges, and to about 1200 metres in the north and east ranges. Sunday is forecast to be cooler and drier. Expect flurries and light snowfall in most areas of the interior. The timing of the next system is difficult at this time, but we should see some more snow on Monday or Monday night.
Avalanche Summary
Some small loose snow avalanches up to size 1.0
Snowpack Summary
The new snow load is building faster in the northern ranges of the interior than it is in the southern and eastern ranges. The depth of the new storm snow above the various old surfaces is what is driving the danger ratings at this time. Large surface hoar and near surface facets are widespread above various crusts and hard wind slabs. Observers are still able to find the early November surface hoar layer. This layer has not been reactive during the recent long dry spell. Tests show that it is getting harder to pull the snowpack apart at this interface. We may still see this layer become active again if we get the right combination of load and warm temperatures. Going down deeper, we still need to consider the interface between the snow that did not melt over the summer, the glacial ice, and the October rain event. If this deeply buried beast wakes up, we may see very large avalanches in high alpine north and northeast aspects. In areas with a shallow snowpack, the weak basal layer of facets will be a concern with any added load.
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.
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
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.