Regions
Kootenay Boundary.
Confidence
Fair - Due to variable snowpack conditions for the entire period
Weather Forecast
Tuesday and Wednesday: Possible sunny breaks with isolated flurries, winds light from the northwest and alpine temperatures -5. Freezing level rising to 800m on Tuesday.Thursday: Light snow, winds light from the southwest and alpine temperatures of -6. Freezing level 900m.
Avalanche Summary
A natural cycle began on Friday and continued on Saturday, with several slabs to size 2.5 failing on all aspects. Many were triggered by wind-loading. They failed within the storm snow or on the mid-Feb surface hoar or crust layers.
Snowpack Summary
In much of the region, up to 65 cm recent snow overlies weak interfaces buried in mid-February (mainly surface hoar/ sun crust layers). The storm slab above these interfaces has the potential for wide propagations and surprisingly large avalanches, especially where winds have shifted the snow into slabs in the lee of terrain breaks. A thin freezing rain/rime crust formed on Friday, which is now buried by about 15 cm snow. Snow forecast overnight Sunday and on Monday will add to these storm slabs.In the Rossland Range, surface hoar which was buried mid-week is 20-30 cm down and exhibits easy, sudden results in snowpack tests. As more snow builds over this layer, it could become touchy.Older snowpack weaknesses buried in the upper snowpack (Feb 4th and Jan 23 surface hoar/facet/sun crust layers) are still being tracked by professionals. There is some potential for triggering one of these deeper layers with a large trigger like an avalanche in motion, or from a thin-spot trigger point. The lower snowpack is generally well settled.
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.