Avalanche Forecast

High -

Tuesday: The ridge of high pressure will slowly move off as the next system rolls in. This will bring mostly cloudy skies, 5-10 cm of new snow and moderate ridgetop winds from the southwest. Wednesday: Snow 10-20 cm on average through the region. Moderate to strong southwest winds and freezing levels near 1300 m. Thursday: Cloudy with isolated flurries. Westerly winds generally light with strong gusts and the freezing levels fall to 1000 m.

On Sunday, storm slabs and wind slabs up to size 2 occurred naturally while several human and explosive triggered slab avalanches up to size 1.5 were reported. At this point there isn't much snow overlying the weak layers in the upper snowpack, however, you can expect avalanches will be likely during and just after the forecast storm on Wednesday/ Thursday as the buried weak layers are persistent and adjust to more load.Given the weak nature of the snowpack, the main concern remains the possibility for triggering large deep persistent slab avalanches. Large and very large (size 2.5-3.5) avalanches have been reported regularly over the past few weeks. Two weeks ago, a group of snowmobilers triggered a fatal avalanche near Invermere, also on the basal weak faceted grains. The avalanche was on a south aspect and ran approximately 900 to 1100 m. Two snowmobilers were fatally involved in this slide. Check out the Forecaster Blog for more information on the deep persistent weak layer.

The snowpack in this region is complex, weak and touchy, with very large avalanches easily triggered from specific terrain features. Those features are typically were people want to ski or snowmobile which makes decision making and managing this risk tricky. Up to 20 cm of recent snow has buried large surface hoar crystals and/or sun crusts. This will likely develop into a touchy problem as more snow accumulates. The most suspect terrain features will be steep slopes and rolls between 1500m- 2000 m (where the largest surface hoar exists) and steep south-facing slopes in the alpine (where sun crusts exists.The weak nature of the snowpack lies at depth. The base of the snowpack is also composed of weak faceted grains and a crust in many parts of the region. Humans have and will continue to be able to trigger these layers in areas where the snowpack is shallow.