Avalanche danger is increasing as the new storm moves in from the Southwest.
Confidence
Fair - Freezing levels are uncertain
Weather Forecast
Light snow (5-10 cm) overnight combined with moderate Southeast winds and freezing levels around 1000 metres elevation. Flurries with periods of light snow during the day on Friday combined with moderate to strong Southwest winds. Freezing levels expected to rise up to about 1400 metres on Friday. Light snow (3-8 cm) by Saturday morning and continued snowfall (10-15 cm) during the day Saturday as freezing levels continue to rise and Southwest winds increase to strong-very strong. Freezing levels are forecast to spike up to about 2000 metres by Sunday morning combined with 10-20 mm of precipitation and very strong Southwest winds. This may be rain up into the alpine.
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. Conditions in the Coquihalla area are quite different to the Duffey/Hurley regions. Reports from the Coquihalla suggest there's less than 1 m of snow in most avalanche areas. On the surface, fairly widespread surface hoar development has been reported. Below this, a small amount of recent storm snow overlies a thick rain crust. In the north, we have very limited observations. That said, I expect a deeper, more complex snowpack where well settled storm snow overlies a mix of crusts and facets 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.