Regions
Kootenay Boundary.
Time to be extra cautious in avalanche terrain. Deep weak layers are under stress and have been producing large avalanches recently.
Weather Forecast
SUNDAY: Sunny, moderate northwest winds, alpine temperatures around -8 C.MONDAY: Mix of sun and cloud, light winds, alpine temperatures around -5 C.TUESDAY: Afternoon flurries with 5-10 cm, light southwest winds, freezing level climbing to 1500 m with alpine temperatures around -2 C.
Avalanche Summary
Initial reports from Saturday include numerous natural and skier triggered loose wet avalanches at lower elevations (size 1.5) . Reports from Friday include several large natural avalanches including a size 3 persistent slab in the Rossland range and up to size 3.5 deep persistent slabs in the Valhallas (failing on basal facets over 2 m deep).The upper snowpack should stabilize with cooler temperatures, but deeper persistent weak layers remain under heavy stress and have the potential for large and surprising avalanches.
Snowpack Summary
Rain has soaked the upper snowpack for a second time in a week. This time all the way to mountain tops. Cooling temperatures will gradually form a rain crust on the surface, but expect a thick layer of moist snow in the upper snowpack for some time. This heavy snow will stress a number of deeper weak layers including the late-February facet / surface hoar interface (70-120 cm deep), the mid-February crust (90-130 cm deep), and basal facets in shallow snowpack areas.
Problems
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.