Avalanche Forecast

Good

Wednesday: Snow flurries with another 5-10cm possible, moderate southwesterly winds becoming northwesterlies in the afternoon, and freezing levels are expected to rise as high as 1500m on Tuesday night but drop back down to 700m by midday Wednesday. Thursday and Friday: Mainly sunny and dry with light northerly winds and freezing levels in valley bottoms.

Reports from the Coquihalla area on Monday include several natural avalanches up to Size 2 as well as several 20cm thick Size 1 ski-cut slab avalanches on small terrain features. A thin, but relatively wide-propagating avalanche was triggered on Needle Peak in the Coquihalla area on Sunday. You can read the description here. This kind of avalanche is likely to increase in size and destructive potential with additional loading by new snow and wind.

Another 30cm in the Coquihalla area since late Monday brings the storm snow total to over 60cm since Friday, while the Duffey Lake area got around half that much. Weaknesses exist within this recent storm snow as well as at the interface with the previous snow surface, which includes large surface hoar, facets, old hard wind slabs, or a sun crust. Recent compression tests on a north aspect below treeline gave easy sudden planar shears down 23cm, moderate sudden planar shears down 39cm, and hard sudden planar shears down 60cm. No significant weaknesses have been reported recently below this in the mid snowpack layers. Near the base of the snowpack, a crust/facet layer exists, which is now unlikely to be triggered, except perhaps by heavy triggers in steep, shallow, rocky terrain where more facetting has taken place.