Avalanche Forecast

Fair - Freezing levels are uncertain

A front will move over the interior of the province bringing heavy precipitation overnight through Sunday with expected accumulations of up to 30cm of snow.  Unfortunately freezing levels are forecast to spike at the tail end of the storm early on Sunday morning.  Although there is some uncertainty about how warm it will get the worst case scenario is that the region could see a brief period of heavy rain up to treeline before temperatures cool and snow resumes.  Moderate southwesterly winds will prevail through the storm.  The rest of the forecast period will see a clearing pattern as a strong ridge builds that looks to last through the rest of the week.

A widespread natural avalanche cycle is expected on Sunday as the snow pack adjusts to the forecast snowfall.  Avalanche reports from earlier in the week described large avalanches ranging from size 2.5 to 3 releasing on persistent weak layers deep in the snowpack.  This suggests the potential for smaller storm slab avalanches to trigger these deeper layers producing surprisingly large and destructive avalanches.

The forecast precipitation will add load to the layer of large surface hoar or facets that was buried earlier in the week. In many places these week crystals sit above a thin crust which can be found up to about 1900m on north aspects and all the way to ridgeline on south aspects. The deeper crust/surface hoar combo buried in mid-December also continues to be a concern.  Before Sunday’s storm this weak layer could be found between 60 and 120cm down.  While it is now deeper and less likely to be triggered by people, step down avalanche are possible.  Near the base of the snowpack the facet/crust combo formed in November has mostly been dormant but the avalanche cycle expected for Sunday will be a good test of this layer.