There may be a lot of variability between the North and South areas of this region. Time to dig down and find out what the snowpack looks like in your area, and then share your observations with us!
Confidence
Poor - Due to the number of field observations
Weather Forecast
Flurries or light snow overnight combined with strong Westerly winds and dropping freezing levels. Drier and cooler on Monday with periods of broken skies with light Westerly winds. The next storm should move into the region sometime early on Tuesday morning and bring 5-10 cm during the day with strong Southwest winds. The storm should continue overnight and into Wednesday morning, but at this time the snowfall amounts look very light.
Avalanche Summary
Soft slab avalanches were reported during the storm from alpine North aspects up to size 1.5 on Saturday. I suspect that storm slab avalanches continued on Sunday with the additional 20-25 cm of new snow combined with strong winds.
Snowpack Summary
The new storm slab may be 40-50 cm thick in The Coquihalla and is reported to be bonding well to the December 11th crust. In the Coquihalla there is 70-100 cm of snow on the ground above 1600 metres elevation, and below threshold for avalanches below 1500 metres. The recent surface hoar has been reported to have been mostly blown away by the Northeast wind before this new storm. In the North of the region it sounds like the recent surface hoar is 2-4 mm at treeline and up to 30 mm near open creeks below treeline. The knife hard December melt-freeze crust extends up to about 2100 metres and then tapers off to nothing by 2300 metres. The new storm slab may be up to 70 cm in the North of the region, and it may not be bonding well to the old crust/ surface hoar combination. The November crust is deeply buried and may become easier to trigger in isolated areas if the load from the storm slab overcomes the bond at the crust interface.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.