South Columbia

The reactive new storm slab problem expected for Wednesday is the tip of the iceberg. Forecast warming will increase the chances of triggering very large avalanches on deeply buried layers. This is a time to build large safety margins into your terrain selection.

Tuesday night: Cloudy with a storm pulse bringing 15-25 cm of new snow. Light to moderate southwest winds.

Wednesday: Lingering flurries bringing another 5-15 cm of new snow over the day, continuing but easing overnight. Light to moderate southwest winds. Treeline high temperatures around -2 with freezing levels to 1300 metres.

Thursday: Cloudy with isolated flurries and a trace of new snow. Light to moderate southwest winds, shifting northwest by evening. Treeline high temperatures around -1 with freezing levels reaching 1500 metres. 

Friday: A mix of sun and cloud. Light northwest winds. Treeline high temperatures around -3 with freezing levels only reaching 1000 metres.

On Monday, several small skier triggered avalanches were reported across the region. Mostly windslabs, but a few loose dry on slopes that saw the sun, and one lingering storm slab that was sitting on a buried sun crust.

The persistent early December crust/facet layer has recently been active in this region.

On Monday, a few very large simultaneous remote triggered persistent slab avalanches were reported in this Mountain Information Network (MIN) report south of Kaslo. It reported as a near miss, triggered from 150 m away on northeast through southeast features around treeline. The crown was one meter deep and propagated 500 m wide.

On Friday, three naturally triggered size 2-3 avalanches on this layer were reported in mountain ranges just west of the Columbia river. They were reported at treeline and above on south and east aspects. Some were known to be windslab avalanches that stepped down to this deeper, persistent layer in a thin, rocky area. 

15-25 cm of new is expected in the region by end of day Wednesday. This is expected to form a new storm slab problem above a mix of settling storm snow and windslabs in the upper snowpack after several days of consistent snowfall and southwest wind.

Our new snow and 50-90 cm of recent storm snow will be settling on top of weak, faceted snow that formed during the recent cold snap. As new snow accumulates and temperatures rise, the upper meter of the snowpack may become increasingly upside-down and more likely to avalanche. 

We're actively monitoring the early December crust. In some places, it's down 80 cm, while in wind-loaded terrain features it can be found as deep as 180 cm below the surface. It consists of faceted grains above a bulletproof crust formed by the Atmospheric Rivers of early December. There has been avalanche activity on this crust over the weekend. Larger avalanches in surface layers as well as natural cornice falls may have potential to step down to this layer in the coming days.

• Storm slabs in motion may step down to deeper layers resulting in large avalanches.
• The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
• The likelihood of deep persistent slab avalanches will increase with each day of warm weather.