Additional forecasted snow on an already over-loaded snowpack will keep the avalanche danger elevated. Conservative route choices are essential.
Weather Forecast
Two significant frontal systems are lined up to move inland over the next three days. 25-40 cm of additional new snow is expected along the divide by end of day on Thursday. This snow will be accompanied by moderate to strong SW winds. Freezing levels remain at valley bottom.
Snowpack Summary
40 - 60 cm of recent snow overrides a weak interface (Dec 10 layer) consisting of facets and surface hoar. Fresh windslabs can be expected on lee (north and east) aspects. The lower snowpack is weak and facetted. Any avalanches initiated in the storm snow have potential to step down to this lower layer.
Avalanche Summary
Numerous natural and skier (or explosive) triggered avalanches up to 2.5 have been reported over the past few days. Avalanches may run further down slope than expected, so be cautious of overhead hazard.
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.