Avalanche Forecast

Moderate - Timing or intensity of solar radiation is uncertain on Sunday

Mostly clear overnight with light westerly winds and freezing down to valley bottoms. Mostly clear with strong solar radiation on Sunday (chance of valley cloud) with cloud developing in the late afternoon. Light southwest winds and freezing levels climbing up to 1400 metres. Light snow starting overnight and continuing on Monday with moderate westerly winds and daytime freezing levels climbing from valley bottoms up to 1300 metres. Clear on Tuesday as the ridge re-develops, temperatures around -10 at treeline overnight.

On Friday we had reports of natural, skier controlled, and accidentally triggered storm slab avalanches up to size 2.5 from both the Monashees and the Selkirks. On Thursday there were reports of natural and skier accidental storm slab avalanches up to size 2.0. On Wednesday a ski cut resulted in a size 3.0 avalanche with wide propagation on buried surface hoar above the February 10th crust. Several small skier accidental avalanches and skier controlled avalanches in the storm snow were also reported. On Tuesday there were several skier accidental avalanches up to size 2.0 that released on the storm slab/crust interface. Skier controlled storm slab avalanches up to size 1.5 were mostly on east aspects at treeline. On Monday we had reports of natural wind slab and storm slab avalanches up to size 3.0 and accidentally triggered slab avalanches up to size 1.5.

Strong solar radiation may weaken bonds within the storm snow or at the crust that is now down 60-90 cm. These storm slabs are sitting on a buried melt-freeze crust on east thru west aspects in the alpine, and on all aspects at treeline. In some areas there is a weak layer of surface hoar at the interface between the storm snow and the crust, that we are going to call a new persistent weak layer. We are going to seperate this from the storm slab problem because there are some weak layers within the top layers of the recent storm snow. Moderate winds have created areas of wind slab in the lee of west or southwest winds that may be close to a metre deep. Wind slabs in motion may trigger the persistent weak layer on the crust and result in wide propagations and very large avalanches. The bond between the recent storm snow and the crust is variable across the region, east thru southeast aspects have been the most reactive over the past few days. Surface hoar buried in early January now lies up to 200cm below the surface and has become less of a concern. Possible triggers for this deep and destructive layer include a large cornice fall or significant warming.