North Columbia

Sunshine and warming are set to maintain heightened avalanche danger over the coming days. There's a lot of new snow on the ground to feed both slab and loose wet avalanche problems.

Moderate - Timing or intensity of solar radiation is uncertain

Wednesday: A mix of sun and cloud. Light south winds. Freezing level rising to 1700 metres with alpine high temperatures around -5.Thursday: A mix of sun and cloud. Light south winds. Freezing level to 2000 metres with alpine high temperatures around -2. Weak overnight cooling.Friday: Cloudy with light flurries and a trace of new snow, increasing overnight. Light southwest winds. Freezing level to 2000 metres with alpine high temperatures around -1.

Reports from Monday were limited by poor visibility but included one small (size 1, 20 cm deep) ski cut wind slab as well as skier-triggered loose snow releases on steeper slopes. The rough dividing line between loose wet and loose dry activity was about 2000 metres.Sunday's warm weather, rain and sunny breaks produced a widespread loose, wet avalanche cycle from size 1.5-3 on steep, solar aspects from 1600-2600 m, in the afternoon.Saturday there were reports from the southeast corner of the region of natural cornice and storm slab avalanche activity (size 2-3) on north and west aspects from 2500-2700 m.On Friday a large cornice collapsed on a southeast aspect at 2500 m, with several 'bus-sized' blocks observed in the debris.Thursday there were reports from Glacier National Park of a size 4 wind slab that occurred overnight and is thought to have been cornice triggered on a north aspect at 2800 m.

About 30 cm of recent storm snow overlies a crust on all aspects to at least 2300 m (and possibly higher on south aspects). While 40-50 cm of storm snow can be found at higher elevations in the alpine. Below 2200 m this new snow has a surface crust becoming moist or wet by the afternoon.Within the upper snowpack there are now a few different crusts with only the shallowest of these remaining a concern as the uppermost layer of storm snow settles and bonds to it.There is some lingering concern around the mid-March Persistent Weak Layer (PWL) in the alpine where it is found 90 to 120 cm below the surface. This buried crust/surface hoar interface was widely reactive but has not produced any avalanche in the past week. It is likely trending towards dormancy, but we need to keep it in the back of our minds as it is capable of producing large avalanches should it be triggered (think step-down from a surface avalanche or a cornice collapse).Deeper persistent weak layers from December and January are generally considered dormant at this time but may be starting to become reactive to large triggers, such as a cornice collapse.