Regions
Northwest Coastal.
Storm slabs continue to develop at all elevations. Deep pockets of wind transported snow may exist at higher elevations.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Another pulse of moisture should bring 5-10 cm overnight by Monday morning combined with moderate westerly winds. Light snow on Monday with freezing levels around 300 metres. Another 10-15 cm by Tuesday morning as yet another imbedded system moves along with the cool northwest flow. On Wednesday the freezing level should drop down to valley bottoms with light northerly winds and a chance of broken skies. Outflow winds may start up on Wednesday if the arctic air moves closer to the coast.
Avalanche Summary
Several small naturals were reported from steep rock slabs at low elevations above the highway. No new avalanche reported from higher elevations. Suspect travel and visibility may have been restricted by stormy conditions.
Snowpack Summary
There was another 15 cm at Shames and 35 cm a little further west in the 24 hours ending at 3:00 PM Sunday. The north of the region around the east end of the Bear Pass had over 50 cm in the same time period. New snow continues to build the load above buried weak layers. There is 25-35 cm above the December 17th (151217 SH) surface hoar, and 35-50 cm above the December 14th (151214 SH). At this time, the new snow continues to come in cold and dry and may not have the load needed to settle into a cohesive slab above these weak layers. The early December layer buried on the 1st or 2nd (151201 SH) is now down a metre or so depending on your area. This layers distribution is variable. In some areas, this layer may be sensitive to human triggering and wide propagations while in other areas it is non-existent or has gained significant strength. Most of this information is coming from the Shames area or from commercial operations near Terrace. Conditions may be different close to Kitimat, where it looks like recent snowfall amounts may be a bit higher and temperatures a bit warmer.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.