Purcells

Fair - Forecast snowfall amounts are uncertain on Sunday

Another 5-8 cm of snow is expected from flurries during the evening and overnight into Sunday. The freezing level should drop back down to valley bottoms. Sunday is forecast to be a mixed bag of convective flurries and some sunny periods, with the freezing level rising up to about 700 metres. High pressure should have moved well into the region by Monday, bringing mostly clear skies and light north or northeast winds and cooler temperatures. The region should continue to be under the influence of high pressure on Tuesday. Expect clear skies and cold overnight temperatures.

Skier remote and skier accidental avalanches continued to be reported on Friday. I expect that the new snow was not enough to cause another round of natural activity on the Feb persistent weak layer (PWL), but human triggering continues to be likely from light additional loads. Avalanches that release on or step down to the PWL could be very large and destructive.

About 15cm of light new snow and light winds created a blanket of dry light snow above the recent stiff windslabs. The upper snowpack structure is very complex. There are buried layers of surface hoar, buried melt-freeze crusts, and some buried crusts with facets. These weak sliding layers are buried anywhere from 40 - 80 cm by several different storm layers. There are some shears in the storm layers on decomposed and fragmented snow crystals. As the snow above the surface hoar layers settles into a cohesive slab, we are seeing easier and more sudden shears that are a bit deeper. The surface hoar is more likely to produce wider propagations, and lower angle fractures in areas where it is associated with a crust. The crust has been reported to be 2-3 cm thick in some areas. The mid-pack is generally well settled. Basal facets have not been reactive, but operators continue to monitor this layer in tests. Triggering this deep persistent weak layer is unlikely, but shallow snowpack areas or shallow weak areas adjacent to deeper wind loaded slopes are the most suspect locations.