South Columbia

Fair - Freezing levels are uncertain on Friday

Thursday, Friday, and Saturday are forecast to be mostly clear and sunny with freezing down to the valley at night and rising slightly above the valley during the warmest part of the day. The freezing level on Friday may rise up to about 1200 metres. These conditions are prime for surface hoar to develop and continue to grow. We may continue to develop sun crust on steep slopes in the alpine that are exposed to the sunshine. Winds should be light from the west, but we may see some moderate outflow winds from the north in the alpine.

It is always important to know the history of the snowpack in the area that you want to explore. This season presents some challenges developing this baseline information due to the snow arriving well before most observers have started working in the field. It may be wise to take the time to dig down deep and see what the basement looks like in your regular play areas. There was one size 2.0 skier triggered slab avalanche in the South Selkirks that we know about from Monday. The slab was released by the third or fourth skier in a group, from a steep south aspect near the ridge top in the alpine. There are a few more reports from yesterday of old large avalanches that probably released around November 27th.

The Surface Hoar continues to grow due to the clear and cold nights. Expect to find a sun-crust that has formed in the alpine on south through west aspects. I expect that the surface hoar will no longer be present on aspects that have developed the sun-crust. Wind slabs persist in the alpine and in large openings at treeline. The windslab has become less reactive to human triggers; however avalanches up to size 2.0 are still possible due to this problem. Some areas have a rain-crust below treeline from the 28th of November that has been buried by about 20 cms of snow. This rain-crust may be developing facets, and could become a layer of interest after it is buried by more of a load. There is still some concern associated with the early November buried surface hoar layer. This layer is buried down about 100-150 cms. Tests are showing that this layer is getting harder to release, and less likely to give clean and fast shears (Sudden Planar). If an avalanche does release on this layer, it is likely to be very large and destructive. Some areas also have a weak layer of facets at the base of the snowpack.