Regions
Kootenay Boundary.
Touchy storm slabs are reactive to human triggers. Use small slopes with low consequence to test the bond of the storm snow.
Weather Forecast
Seasonal temperatures and isolated flurries through the weekend. Significant warming Monday onwards. SATURDAY: 5-10cm possible by Saturday morning. Mostly cloudy with isolated flurries. / Light to moderate southwesterly winds/ Freezing level around 1000 m / Alpine highs to -7 Celsius SUNDAY: Cloudy with sunny breaks / Light, southwesterly winds / Freezing level around 700m. MONDAY: Mainly cloudy, warming significantly with highs to +1 Celsius / Light southwesterly winds / Freezing level rising to 1500 m in the afternoon.
Avalanche Summary
A widespread natural avalanche cycle (to Size 2.5) occurred on all aspects and elevations at treeline and above from Thursday into Friday.
Snowpack Summary
Another 20-30 cm of wet snow fell up to 1800m on Thursday and sits on top of the 45-85cm of recent storm snow: This has created touchy storm slabs at all elevations and aspects. Snowfall amounts have been highest around Kootenay Pass. These slabs have been reported as very reactive to human triggers and are sitting on a variety of surfaces; including scoured surfaces in wind exposed terrain, surface hoar (size 2-3 mm) in sheltered locations, and sun crust on steep solar aspects. Snowpack tests near the Valhallas have given moderate, propagation-likely results down 50-70cms on the Feb 3rd interface. Areas with a shallower snowpack (less than 150 cm) have a generally weak snowpack structure with sugary facets near the ground. This includes shallow alpine slopes and most of the Rossland range. It is possible for storm slab avalanches to step-down to these deeper weak layers, resulting in large, destructive 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.