Variable snowfall amounts are expected on Wednesday. Correspondingly, there may be quite a lot of local variation in avalanche danger.
Confidence
Fair - Forecast snowfall amounts are uncertain for the entire period
Weather Forecast
Wednesday: Moderate to heavy snow (15-25 cm, mostly in the west). Strong SW winds. Alpine temperature near -4.Thursday: Light snow. Moderate W winds. Alpine temperature near -14.Friday: Light snow. Light winds. Alpine temperature near -12.
Avalanche Summary
On Monday, skiers triggered several small soft slabs and sluffs on wind-loaded or steep terrain. Explosives testing triggered three large (size 2-3) slabs within the storm snow. On Sunday, a natural cycle to size 2.5 was observed in the Bugaboos on a variety of aspects in the alpine.
Snowpack Summary
Forecast storm snow is expected to create new slabs. Recent storm snow was shifted into reactive slabs by strong SW-NE winds on Monday. In some areas, the new snow was sluffing fast and far. Deep storm slabs which formed last week are slowly gaining strength. Cornices are large. A weak layer of surface hoar and/or a crust sits about 50-120 cm below the surface. It’s of most concern at alpine and treeline elevations and exhibits variable results in snowpack tests. At low elevations, a supportive crust above this layer means it's difficult to trigger. This layer may linger with ‘low probability/ high consequence’ type character. Testing for this interface in your local area should help you gain (or lose) confidence before committing to aggressive terrain. A facet/crust layer sits at the base of the snowpack in some places.
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.