Avalanche danger rising to HIGH as the storm slab continues to develop.
Confidence
Fair - Freezing levels are uncertain
Weather Forecast
Expect another 10-15 cm of new snow combined with strong Southerly winds overnight. Snow and strong Southwest winds should continue during the day on Saturday resulting in another 15-25 cm by evening. Freezing levels may rise up to about 1500 metres by Saturday evening. Very strong Southwest winds and another 15-25 cm overnight into Sunday morning with freezing levels dropping slightly overnight to about 1100 metres and then rising back up to about 1500 metres on Sunday afternoon as another 5-10 cm of new snow arrives. Yet another pulse of precipitation looks like it will bring 5-10 cm of new snow combined with moderate winds by Monday morning.
Avalanche Summary
No new avalanches have been reported. Expect new storm slab avalanche activity to increase as the storm develops.
Snowpack Summary
A new storm slab is expected to develop above the mix of current surfaces which include a mix of stubborn wind slabs and settled storm snow in the alpine, and a hard rain crust at lower elevations. Surface hoar growth has been reported in sheltered areas. There is still concern for a buried crust/facet layer which formed in November.
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.