Avalanche danger is increasing as the new storm moves in from the Southwest.
Confidence
Fair - Freezing levels are uncertain
Weather Forecast
Snow starting today and continuing overnight should bring 15-25 cm above 1000 metres elevation. This snow will be combined with strong South to Southwest winds. Light snow (5-10 cm) and strong to very strong winds during the day on Friday combined with slightly higher freezing levels (around 1200 metres). Very strong South winds and heavy snowfall (25-35 cm) starting Saturday morning combined with forecast freezing levels climbing up to about 2000 metres. Expect another 20-30 mm of precipitation by Sunday morning before the freezing levels start to drop. This may be rain up into the alpine.
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.