Forecast new snow and wind are expected to result in Considerable avalanche danger. If you see more snow than forecast in your area, then consider these danger ratings to be a bit low.
Confidence
Poor - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Strong to very strong Southwest winds overnight combined with 10-15 cm of new snow and freezing levels rising up to 1300 metres. Snow ending Sunday morning with a chance of flurries during the day combined with strong Westerly winds and freezing levels rising up to about 1600 metres. Drier and cooler on Monday as a weak ridge of high pressure builds over the region. The next pulse of moisture is forecast to move in from the coast sometime on Tuesday. Models are not in agreement with regard to timing, location, or intensity.
Avalanche Summary
No new reports of avalanches. Expect new storm slab avalanches to increase as the new storm develops.
Snowpack Summary
The new storm is expected to develop a storm slab above the mix of old surface forms that include hard crusts, near surface facets, and surface hoar. In the Coquihalla there is 65-80 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 40 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.