Forecast snowfall amounts are uncertain. Some upslope areas like the western Monashees may see enhanced snowfall and these danger ratings may be one level too low.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
Moderate snow (5-10 cm) and moderate to strong westerly winds overnight with the freezing level dropping to valley bottoms. Light snow during the day Friday becoming moderate snow in the evening. Snow will be combined with moderate westerly winds and freezing levels rising up to 1400 metres. Some chance of sunny breaks during the day on Friday. Flurries or light snow during the day on Saturday with light winds and freezing levels climbing from valley bottoms up to 1400 metres. Mostly clear on Sunday with light winds and freezing levels climbing from valley bottoms up to 1400 metres.
Avalanche Summary
Early reports on Thursday from the western Monashees that natural, skier controlled and skier accidental avalanches were releasing in the 25 cm of new snow that fell during the day. 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.
Snowpack Summary
Recent new snow and wind have developed storm slabs that are 50-80 cm deep. 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. 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 storm slab 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.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.