Regions
Kootenay Boundary.
Heads up! Large avalanches from above have the potential to reach run-out zones.Special Avalanche Warning in effect for the interior ranges. Copy this address to view details: http://bit.ly/2nSOUyX
Weather Forecast
The weather pattern has taken a dramatic shift as the arctic ridge becomes the dominant weather feature through the weekend, bringing colder temperatures and mostly clear skies.Saturday: Mostly sunny. Alpine temperatures near -8 and freezing levels at valley bottom. Ridgetop winds light from the West. Sunday: Mostly cloudy. Alpine temperatures near -9. Ridgetop winds light from the northwest.Monday: A mix of sun and cloud. Alpine temperatures -10. Light winds from the northeast.
Avalanche Summary
On Thursday, numerous large and destructive natural slab avalanches occurred through the region up to size 4 on all aspects and elevations. Avalanche control using explosives triggered numerous loose wet avalanches up to size 2 and a significant size 3 storm slab avalanche. These were reported from SE-SW slopes above 1900 m. Natural avalanche activity may spike again with the first hit of sun then start to taper off through the weekend with colder temps; however, slopes will remain primed for human triggers.
Snowpack Summary
Storm snow accumulations vary, showing 10-45cm across the region at upper elevations. Below 1800 m a surface crust exists. The new snow in the alpine has been redistributed to leeward slopes from strong northwest winds. This now brings 1- 2 m of settled snow sitting on three significant surface hoar/ crust layers that were formed early to mid-January, and back in December. Near the base of the snowpack a crust/ facet interface exists and will likely haunt us all season. These persistent weak layers that lurk within the snowpack are reactive, producing large and destructive avalanches. The snowpack is extremely complex and requires respect and diligence at this time.
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.