Regions
Kootenay Boundary.
New storm slabs may continue to be reactive, and deeply buried persistent weak layers may continue to be triggered in isolated terrain features.
Weather Forecast
Unsettled with flurries or periods of light snow overnight combined with moderate westerly winds. Expect 3-5 cm by Sunday morning, and not much more accumulation during the day on Sunday. Freezing levels staying below about 500 metres on Sunday as the winds become light from the northwest. Some chance of broken skies on Sunday producing brief periods of moderate solar radiation. Overcast with convective flurries on Monday with light winds and alpine temperatures around -10. Tuesday should be a bit cooler with light winds and broken to scattered cloud.
Avalanche Summary
Some small natural wind slab or storm slab avalanches up to about 20 cm deep were reported on Saturday from the south of the region. On Friday a couple of operations reported natural slab avalanches up to size 2 that were releasing as pockets of wind slab or thin storm slab. Explosives controlled avalanches up to size 2.0 releasing in the storm snow were also reported on Friday. No new reports of any avalanches releasing down to the persistent weak layers.
Snowpack Summary
There was another 5-10 cm of new snow on Saturday morning that had been transported by moderate westerly winds overnight. This new snow has added to the 10-20 cm of new snow that was reported on Friday. The total recent storm slab of 15-30 cm may be sitting on a layer of surface hoar that was buried on January 27th, or on top of one or two thin freezing rain crusts up to about 2100 metres. Some areas report that previous strong winds destroyed this new layer of surface hoar, and may have stripped the old surface back to a hard rain crust before the new storm snow arrived. The persistent weak layer that was buried January 4th is now down 80-120 cm and continues to give sudden planar fractures in snowpack tests in some areas.
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.