Regions
Northwest Coastal.
The storm surges on! Continue to avoid all avalanche terrain on Sunday during periods of heavy loading from rain, new snow and wind.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain on Sunday
Weather Forecast
A frontal system impacting the coast is expected to continue to deliver moderate precipitation and strong southwest wind through Saturday night. Continued snow and wind in more modest quantities is expected on Sunday and Monday before the ridge rebounds on Tuesday. SATURDAY NIGHT: Freezing level 1400m at sundown, decreasing through the night. 10 to 25cm of snow possible, strong to extreme southwest wind.SUNDAY: Overcast, freezing level around 600m, moderate to strong west/southwest wind, 3 to 15cm of snow. MONDAY: Overcast, freezing level around 500m, moderate to strong southwest wind, 2 to 10cm of snow. TUESDAY: Scattered cloud cover, freezing level at valley bottom, light variable wind, no new snow expected.Visit avalanche.ca/weather for a more detailed mountain weather forecast.
Avalanche Summary
On Friday wet slab avalanches to size 2 were reported from steep terrain where the ground cover consists of smooth rock slab. These avalanches went to ground. It is suspected that natural avalanche activity continued through the day Saturday.
Snowpack Summary
The region picked up 15 to 40cm of storm snow Friday evening into Saturday morning, and new snow fall continues to fuel storm slab development as of Saturday afternoon. These new storm slabs rest on a rain saturated snowpack between valley bottom and 800m. Above 800m the new storm snow rests on settled old snow, or a variable melt freeze crust. In some areas a feathery surface hoar layer down 50 to 60cm was producing moderate snowpack test results. Down 70 to 100cm lies a 5 to 10cm thick crust which was buried on November 23rd. There is a second crust that is associated with facets that was buried at the end of October, look for this widespread interface down around 100 to 200cm below the surface.
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.