Avalanche Forecast

Fair - Timing, track, or intensity of incoming weather system is uncertain

Snow starting overnight or early Thursday morning combined with strong Southwest winds and alpine temperatures near -5. Expect 10-20 cm by early afternoon on Thursday and another 10-15 cm overnight by Friday morning. Strong Southwest winds on Thursday becoming very strong Southerly on Friday as warm Pacific air is pushed up and over the cold arctic air to the North. The North and East of the region may see enhanced snow fall due to the cooling effect of the arctic air. The South and West of the region may see freezing levels rise up to 2000 metres that may result in rain up to treeline elevations. The storm should continue on Saturday with another pulse (15-25 cm) of warm and moist air pushed by moderate Southwest winds.

There were numerous size 1.5 natural and skier triggered avalanches reported from Tuesday. In some areas pockets of wind transported snow were easy to trigger up to size 1.5 at ridgetops where they were sitting on a hard crust. I suspect continued loading from the forecast snow and wind over the next few days may result in widespread natural activity within the storm slab, or on the crust that was buried at the end of January. Storm slab avalanches in motion may result in persistent weak layer avalanches which may be large and destructive.

Thin new slabs may not be bonding well within the storm snow. Pockets of wind transported snow at ridgetops may be easy to trigger where they are sitting on the crust that formed last week. The new storm slab is up to 40 cm thick and sits above a variety of old surfaces. The old surfaces include the crust that formed last week, a new layer of surface hoar that developed during the clear weather late last week, and in some places wind slabs that developed smooth hard surfaces. Deeper in the snowpack the mid-January surface hoar remains a concern. It can be found down 60-120 cm across the region, but in most places it is about one metre down. In some locations it has reportedly gained quite a bit of strength, but elsewhere it is still producing sudden collapse (popping) failures in snowpack tests. The mid-December surface hoar layer is now 80 to 140cm below the surface and has become unlikely to fail, the storm at the end of the week should be a good test to see if it will become active again.