Although the trend shows improvement the potential for triggering an avalanche is greatest at higher elevations due to recent heavy snowfall and strong winds.
Weather Forecast
A ridge of high pressure will build over BC resulting in much drier and cooler weather for the next few days. Most areas should see a mix of sun and cloud with slight chance of the odd flurry. Freezing levels should gradually drop to 500-1000 m on Saturday and to valley bottom for Sunday and Monday. Winds ease off and become light and variable.
Avalanche Summary
Widespread natural avalanche activity up to size 3 was reported on Wednesday and Thursday. These consisted of deep storm slabs, particularly from wind loaded slopes in the alpine, and wet slabs or loose wet sluffs at lower elevations. Some of the wet slides gouged down to the ground. Natural avalanche activity should taper off as conditions cool and dry out, but it could still be possible to trigger storm or wind slabs at higher elevations where most of the recent precipitation fell as snow.
Snowpack Summary
Warm temperatures and rain have resulted in wet snow up to at least 1900 m and moist snow even higher. Strong southerly winds have loading leeward features in the alpine. Below the new storm snow (~30-60 cm) may be a layer of surface hoar which was buried on Dec 5. Another weak layer of surface hoar and/or facets can be found 80-100 cm deep in some locations. This layer has produced easy or moderate "pops" results in recent snowpack tests. A thick rain crust with facets from early November is buried over 1 m down. Snowpack tests on these deep weak layers are showing slowly improving results, but in some locations these layers are still reactive and have the potential to release large slab avalanches.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.