North Columbia

Cornice falls have been responsible for most of the avalanches reported in the past few days. Storm slabs or cornices may trigger persistent weak layers resulting in large avalanches.

Moderate - Forecast snowfall amounts are uncertain on Thursday

Overnight: 5-10 cm of new snow with moderate southerly winds and freezing down to 1300 metres. Thursday: 10-20 cm of new snow with moderate southerly winds and daytime freezing up to 1800 metres. Friday: Freezing down to 800 metres before a mix of sun and cloud brings the freezing level back up to 2000 metres with light winds. Saturday: Overcast with 3-5 cm of new snow and light winds. A cooling trend should start to drop the daytime freezing levels.

Natural cornice falls up to size 3.5 continued to be reported on Tuesday. Natural storm slab avalanches up to size 2.5 were reported on Monday from the Selkirks. Natural storm slab avalanches up to size 3.0 were reported on Sunday from both the Monashees and the Selkirks.

New snow is forecast to develop new storm slabs in the alpine and at treeline. These new storm slabs are developing above a mix of old surfaces that include melt-freeze crusts on solar aspects in the alpine, and all aspects at treeline. In some areas the new snow may hide some lingering wind slabs that are left from the last stormy period. The biggest problem lately has been large and fragile cornices that have regularly fallen off naturally with loading from wind, or due to warming from direct sun or daytime heating. The February weak layers are down about 160-200 cm and the deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack. These deep weak layers have been released with large triggers like cornice falls, and they may be more likely to fail on southerly aspects during periods of strong solar radiation or from heavy loading from storm snow. Expect cornices to experience new fragile growth during the next few stormy days.