Avalanche Forecast

Following a rapid warm-up for the south of the region, significant snowfall and strong wind are expected to impact the north of the region on Friday.

Wednesday night: Mostly clear, moderate south wind increasing to strong above 2000 m, freezing level dropping below 800 m in the north and staying near 2000 m in the south of the region.

Thursday: Increasing cloud, moderate to strong southerly winds, freezing level 1600 m in the north and 2200 m in the south.

Friday: Overcast, 15-35 cm of new snow, with higher totals falling in the northern half of the region, moderate to strong south winds, freezing level dropping from 1500 m to 500 m.

Saturday: Mostly cloudy, isolated flurries with trace accumulations, moderate southwest winds, freezing level near 1300 m.

In the north of the region, a large (size 2) natural wind slab avalanche was observed on a southeast aspect at 2250 m, breaking 40 cm deep. Observers in the Duffey Lake areas also reported a large (size 2.5) avalanche on a north aspect at 1750 m that was thought to have released 1 m deep on a persistent weak layer. On Sunday, a size 1.5 skier accidental was reported on a northwest aspect in the alpine near Duffey Lake. The slab is thought to have failed on a thin layer of underlying facets over the firm bed surface of old, previously wind-stiffened snow. 

in the Coquihalla area Monday, natural glide slab avalanches size 2-2.5 were observed out of steep north facing paths below treeline. Glide slabs are notoriously difficult to forecast but with the warming trend ahead, we may see an uptick in activity. Glide slabs are most likely in areas of smooth ground cover such as rock slabs at lower elevations experiencing prolonged warm temperatures with limited overnight refreeze. These avalanches will be large, involving the full depth of the snowpack. Carefully consider your access/egress routes where they cross under large paths. 

Over the weekend, the Coquihalla area saw heavy skier traffic. While most reports described good ski quality in the trees, one MIN reported a skier triggered wind slab on a northeast aspect around treeline.

Above freezing temperatures are forecast to reach 2200 m in the south of the region on Thursday with added intensity from strong sun. This rapid warm-up is expected to initiate wet loose avalanche activity and destabilize cornices. Watch for pinwheels and roller balls, as they are a clear indication of this problem. You can avoid them by staying off steep slopes when the snow becomes wet or slushy. Read more about the effects of warming on the snowpack in the Forecaster Blog. 

Upper elevations are wind affected throughout the region.

• In the Coquihalla area, the snowpack is generally well consolidated with no concerns of buried weak layers.
• In the north of the region, 15-30 cm of snow sits over a widespread layer of facets and isolated crusts. This interface is of most concern in areas where a thin layer of facets separates recent wind slab (above) and old buried hard slabs (below) which can act as a bed surface.
• A persistent weak layer composed of a crust, facets or surface hoar depending on elevation/aspect is now down 70-120 cm. This layer, buried in late January, continues to be noted in snowpack tests with mixed results. There have been no recent avalanches reported on this layer. Large triggers, such as an avalanche in motion, cornice fall, or intense loading from snow/ wind and/or a rapid rise in temperature can awaken these deeper weak layers. The lower snowpack is well settled and strong in most areas.

• Back off slopes as the surface becomes moist or wet with rising temperatures.
• A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
• Avoid lingering or regrouping in runout zones.
• Cornices become weak with daytime heating or solar exposure.
• Recent wind has varied in direction so watch for wind slabs on all aspects.