South Columbia

The snowpack in the Columbias is both complex and dangerous. Watch for wind loaded areas in the alpine but be especially wary of sheltered terrain at all elevations. This shelter is what has preserved our deeply buried weak layers.

Moderate - Forecast snowfall amounts are uncertain

Wednesday night: Flurries bringing 5-10 cm of new snow. Light to moderate south winds.Thursday: Mainly cloudy with continuing scattered flurries bringing approximately 5 cm of new snow. Light southwest winds. Alpine high temperatures around -8.Friday: Cloudy with scattered flurries and 2-5 cm of new snow. Light southwest winds. Alpine high temperature to -9.Saturday: Cloudy with flurries bringing 5-10 cm of new snow. Light southeast winds. Alpine high temperatures to -8.

Reports from Tuesday included numerous storm slab and wind slab releases ranging from Size 1-2, as well as several more persistent slab releases ranging from Size 2-2.5. This activity occurred on all but southwest aspects and mainly above 2100 metres. One persistent slab was skier triggered on the late November layer, down only 60 cm in an alpine location west of the Valhallas.On Monday, there were many reports of Size 1-2 storm slabs triggered by skiers, generally on northerly and easterly aspects at all elevation bands. Below treeline, avalanches were releasing in open cutblocks. There were also numerous reports of large (size 2 to 3) persistent slab avalanches being triggered naturally and by skiers on northerly and easterly aspects, at treeline and alpine elevations, releasing on the early-January weak layer. There was one report of a very large avalanche (size 3.5) releasing on either the mid-December layer or the November layer.Similar avalanches have been observed daily since last Wednesday. Expect to see more avalanches where these layers are preserved, such as in sheltered locations in the alpine and treeline elevations and in open cutblocks and gullies below treeline.

70 to 100 cm of storm snow sits on a layer of crust and/or surface hoar from mid-January. The crust is widespread, with the possible exception of high elevation north aspects. The mid-January surface hoar is 5 to 20 mm in size and is likely present at all elevation bands. The recent storm snow fell with strong south winds, producing wind slabs in lee features at treeline and alpine elevations and in open areas below treeline.Deeper in the snowpack, the early-January persistent weak layer is buried 70 to 110 cm deep. It is composed of surface hoar on sheltered slopes and a sun crust on steep solar aspects and is present at all elevation bands. Recent snowpack tests have shown sudden fracture characters with moderate loads and high propagation potential, as well as other signs of instability such as whumpfs and cracking. Yet another persistent weak layer buried mid-December is 100 to 150 cm deep and consists of a facet/surface hoar/crust combination. It is most problematic at and below tree line.A rain crust buried in November is 150 to 200 cm deep. While generally considered dormant, occasional activity has shown that it may react in alpine areas where it is less deeply buried.