New snow alert! Looks like a refresh coming our way as moist air from the west collides with cold air from the east. This setup can sometimes result in epic snowfalls, but this time it looks like max 30 cm but cold, dry and light wind. Soft slabs are expected and the avalanche danger will rise. Thursday looks like the best day to ski.
Expect very soft windslabs on Wednesday as light winds redistribute the dry, new snow. These should be easy to observe and test for by choosing small, non-consequential terrain features to check for cracking or fracture propagation. The storm snow will be dry, so any wind will create drifting.
The base of the snowpack consists of weak facets and depth hoar, and there has been some activity on this layer over the past week. Use caution in steep terrain or planar slopes where failures in these basal facets are more likely to propagate. Especially watch thick to thin areas.
Avalanche control teams in Lake Louise and Sunshine Village both reported explosive-triggered windslabs up to size 2 at upper elevations, 30 cm deep fracture lines. Remote triggering was occurring in Lake Louise where hard windslabs were reported. The Parks Canada field team was on the Banff/Jasper highway and did not observe any new slab avalanches.
Expect 5-15 cm of light, dry new snow with minimal wind effect, except at higher elevations, where some windslabs may form. This could overload the Dec 31 surface hoar/sun crust, which will be down about 30-40 cm and may begin to react as the storm accumulates. This storm is unlikely to overload the buried crusts from Dec 22nd and Dec 5th that exist as high as 2350 m. The base of the snowpack remains weak, as the snowpack is well below average.
A shift in weather patterns is underway as a westerly flow of moist Pacific collides with the cold Arctic air over the Rockies. Snow and warming begin Tuesday night and continue through Wednesday, ending early Thursday. Models call for 10 cm, but this could be up to 25 cm in isolated locations. Thursday goes very cold again (-25), but winds should remain light NE through the period. A proper warm-up begins on Friday.
