North Columbia

Recently formed storm slabs are expected to be reactive to human-triggering on Sunday. Conservative terrain selection is critical and it is best to avoid recently wind loaded areas. If the sun comes out, use extra caution on steep south aspects.

Moderate - Due to the number of field observations on Saturday

One last pulse of snowfall is expected to bring another 10-20cm to the region Saturday overnight. Unsettled conditions are expected on Sunday as cold Arctic air begins to move south and replace the recent storm system. Lingering flurries are expected in the morning and sunny breaks in the afternoon. Alpine winds are forecast to be light to moderate from the northwest and freezing levels are expected to fall below valley bottom. On Monday, mostly sunny conditions are expected with light alpine winds from the northwest and treeline temperatures below -10C. On Tuesday, a mix of sun and cloud is forecast with light alpine winds from the northwest and treeline temperatures below -15C.

On Friday, a snowcat was able to trigger three size 2.5 wind slab avalanches by pushing snow off a ridge into steep wind loaded start zones. These occurred on a west aspect at treeline in the Monashees. Ski cutting also produced size 1 wind slabs near ridge top which were up to 20cm thick. On Wednesday, explosives triggered a size 2.5 persistent slab in south of the region on a northeast aspect in the alpine. The slab was 60-100cm thick and released on the crust layer from mid-November. On Sunday, recent storm slabs are expect to remain reactive to human-triggering. These storm slabs should be most reactive on north through east aspects in the alpine as a result of recent wind loading. Persistent slab avalanches on the mid-November crust will remain an ongoing concern and appears to be a low probability, high consequence problem which likely would require a heavy trigger or triggering from a thin area.

Recent snowfall and strong alpine winds from the southwest have formed storm slabs. These slabs are thickest and most reactive in leeward features in wind exposed terrain. In some areas, the recent storm snow may sit over a layer of small surface hoar. There is some uncertainty regarding the distribution of this surface hoar in the region but it was reported in a couple locations in the Monashees west of Revelstoke. The mid-November crust is now down 80-150cm. Test results on this layer have been highly variable ranging from easy to unreactive. While there has not been much avalanche activity on this layer to this point, it has many professionals concerned. It will be important to track how this layer evolves, especially with the upcoming period of cold weather. Below the crust the snowpack is generally well settled and is reported to be moist at lower elevations. Snowpack depths vary greatly throughout the region with an average of 130-200 cm at treeline elevations. Watch out for stumps, rocks, and open creeks below treeline.