Heavy storm snow and strong winds are the driving the danger ratings to HIGH. It's a good time to stick to simple non-avalanche terrain.
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
A strong westerly flow is driving a series of Pacific frontal systems through the Interior regions tonight through the week. Each system will be a bit stronger bringing moderate to heavy snow amounts and strong winds.Sunday Night: Snow 10-20 cm with alpine temperatures -12 and southwest winds 50-80 km/hMonday: Snow 15-25 cm with alpine temperatures near -9 and ridgetop winds southwest 30-70 km/h.Tuesday: Snow 5-15 cm with alpine temperatures -9 and ridgetop winds light from the southwest.Wednesday: Light flurries with alpine temperatures -8 and ridgetop winds 30 gusting to 60 km/h.
Avalanche Summary
On Saturday isolated wind slabs up to size 2.5 were reported. Forecast strong winds and heavy snow will storm slab problems at all elevations.
Snowpack Summary
10-20 cm of storm snow (more to come!) sits over a plethora of old snow surfaces including stiff wind affected snow, faceted (sugary) crystals and surface hoar crystals that formed in locations sheltered from the wind. The new snow will likely have a poor bond to these surfaces. Deeper in the snowpack exist two layers that may become reactive through these next series of storms. The first being a spotty surface hoar layer that sits 30-40 cm down and the mid-November crust buried 90-160 cm deep, depending on elevation and previous exposure to winds. Snowpack tests on the crust have shown variable results from sudden to no result. Tracking and monitoring this potentially weak interface is crucial especially as we move forward into this snowy period where the snowpack will see more load.
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.