Regions
Kootenay Boundary.
Check out the most recent forecasters blog which deals with decision making & the current hazard: http://bit.ly/sF10fT
Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain on Wednesday
Weather Forecast
Tue: Scattered high clouds. Alpine winds light W, switching to mod SW around lunch. 1500m Temp: H: -5, L: -10Wed: A low pressure system tracks S of the int'l border, but will deliver 5 -10cm to the KB throughout the day Wed. Alpine winds Strong W/SW. 1500m Temp: H: -4, L: -15
Avalanche Summary
Up to 50 cm of storm snow from the weekend has formed a soft slab that is reactive to human triggering. Numerous avalanches were triggered by humans & explosives on Sunday, many natural avalanches were reported too. These avalanches were as big as size 2.5 with crowns up to 100 cm in depth. Avalanches triggered in the upper 50 cm could easily step down to the surface hoar layer producing large unmanageable avalanches.
Snowpack Summary
Another 20 cm of dry light new snow on Saturday night and Sunday morning has combined with 30 cm from Saturday morning to add to the load above the highly reactive persistent weak layer (PWL), comprising large surface hoar in sheltered areas and a sun crust on solar aspects. This PWL is now buried by about 100 cm and resulting avalanches could easily be large enough to bury, injure or kill a person. Professionals throughout the region are treating this layer with extreme caution, since it is showing signs of remote triggering and the ability to propagate in low angled terrain. Strong winds last week created stiff windslabs that have been cracking and propagating long fractures. The new snow may make it difficult to identify these windslabs especially in openings at treeline and below. In the alpine there may be enough wind to create new windslabs that are softer and probably will not bond well to the old surface.
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.