South Columbia

Lingering wind slabs are the primary concern for the weekend. However, as the recent storm snow continues to settle, it will be important to continually evaluate the bond between the old snow surface and the storm snow.

High - The weather pattern is stable

Mostly cloudy conditions are expected on Saturday with lingering flurries in the morning and the possibility of sunny breaks in the afternoon. Alpine winds are forecast to be light and treeline temperatures are expected to be around -8C. On Sunday, mostly sunny conditions are expected with light alpine wind and treeline temperatures around -12C. A mix of sun and cloud is currently forecast for Monday with the next storm system arriving Monday night.

On Thursday, explosives triggered a few size 1 avalanches as well as a cornice on a northeast aspect at 2400 m elevation. On Wednesday, ski cutting and explosives triggered storm slabs and wind slabs up to size 1.5 on north and northeast aspects at treeline and in the alpine. These were 10-40 cm thick. No new natural avalanches have been reported since Tuesday. On Saturday, lingering wind slabs which formed during the week are the main concern. The new snow on Friday and Saturday is falling cold and with minimal wind so new problems are not expected to develop. There still remains some concern regarding the mid-December interface that was buried during the recent storm. It appears that in most places the recent storm snow remains relatively low density and has not formed a slab over this interface. The only areas where this layer has been reactive is in wind loaded areas but I would continually watch for signs that a more widespread slab is developing in areas that have not been affected by wind.

50-70 cm of recent storm snow typically overlies the mid-December interface which consists of a variety of old snow surfaces including wind affected snow, faceted (sugary) crystals, surface hoar crystals, and/or a thin sun crust on steep solar aspects. Recent tests suggest the the new snow is well bonded to the interface in many areas. However, where surface hoar has been preserved, the interface is still reactive. In wind affected terrain, the recent storm snow has been redistributed into reactive wind slabs. The thick mid-November crust layer typically sits 1-2 m down in the snowpack. Recent test results on this layer suggest it is generally well bonded to the adjacent snow with the possible exception of shallow snowpack areas. This layer is considered dormant at this time but remains an isolated concern that we will likely be tracking through much of the season.