In the southwest corner of the region there's an unusually weak snowpack. Conditions are primed for people triggering avalanches. Don't let the lure of deep powder draw you into terrain that's inappropriate for the conditions.
Summary
Confidence
Moderate - Due to the number of field observations
Weather Forecast
We're looking at seasonal temperatures, light winds and occasional isolated flurries for most of the week. MONDAY: Cloudy with scattered flurries in the morning. Light northerly wind and freezing level around 800m, alpine high temperatures to -5 Celsius.TUESDAY: Cloudy. Light northerly wind and freezing level around 400m, alpine high temperatures to -4 Celsius.WEDNESDAY: Cloudy with sunny breaks. Freezing levels remaining around 400m and alpine high temps to -4 Celsius.
Avalanche Summary
Preliminary information regarding the backcountry skier fatality on Saturday is that it occurred on a S/SE facing aspect near 2050m in a cross-loaded feature. We had a great MIN report of a cornice-triggered Size 2 on Friday near Cabin Peak in the Bonnington range. The initial failure was in the storm slab on a southeast aspect near 2000m, which stepped down to trigger a weaker layer deeper in the snowpack.We also had a MIN report of a skier-triggered Size 2 on Thursday in the Rossland range. The failure was a deep persistent slab on a cross-loaded west-facing slope, possibly running on mid December facets or even the November rain crust / facet combination.
Snowpack Summary
A complex and tricky snowpack exists in the Kootenay Boundary region. By Sunday morning another 3-12 cm added to the previous 35-55 cm of fresh snow from last week (which was accompanied by moderate to strong southerly winds). This resulted in touchy storm and wind slabs bonding poorly to the previous snow surface that includes facets and large surface hoar on sheltered slopes and/or a sun crust on steep sun-exposed aspects. The Jan 17th surface hoar layer continues to give easy sudden results in snowpack tests (down anywhere from 30 to 60cms depending on location). In some areas of the Rossland range, the mid-November rain crust / facet layer is now likely down 60-100 cm and has become reactive with continued loading and warming. In thin rocky areas, particularly in the Rossland range, recent reports include easy sudden collapse snowpack test results on facets down 120-150 cm near the ground. This deep persistent weakness may also become reactive with continued loading and warming.
mgrist,
Avalanche Canada
