Purcells

Fair - Forecast snowfall amounts are uncertain on Saturday

A ridge of high pressure is expected to move into the region overnight. Northwest winds are expected to continue to be gusty and strong in the alpine and at treeline on Thursday. Some moisture that will remain in the area is expected to cause periods of moderate precipitation alternating with periods of thin cloud. Continued high pressure is forecast for Friday morning, before a low pressure system moves into the region from the Pacific in the afternoon. Southwest wind and moderate precipitation is forecast to begin in the late afternoon or early evening. Snow and wind should continue overnight and into Saturday. The freezing level is expected to drop down to near valley bottoms on Wednesday night, and then rise to about 1000 metres on Thursday.

Avalanches are becoming more frequent and larger. Remotely triggered avalanches continue to be reported. One avalanche was reported as being triggered from 70 metres away on terrain that was only about 20 degrees of slope.

Strong gusty wind has transported snow into a thick slab in the alpine and at treeline. 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 30 - 70 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.