Avalanche Forecast

Fair - Forecast snowfall amounts are uncertain on Saturday

Moderate to heavy snowfall on Friday is expected to continue overnight into Saturday morning. Expect 15-20 cm in the North of the region and closer to 30 cm in the South by Saturday noon. The freezing level should remain at about 800 metres during the storm and then drop down to valley bottoms by Saturday evening. Winds are forecast to be moderate to strong from the South until about midnight and then ease a bit and clock to the west for the morning hours of Saturday. Expect to see some convective flurries on Sunday as a ridge of high pressure slides in behind the storm bringing light northerly winds by late in the day. There may be some sunny breaks on Sunday, and mostly clear skies and cooler temperatures for Monday.

The recent cycle of widespread natural avalanches running on the Feb 08 surface hoar is probably over. Explosive control and human triggering continue to produce avalanches on this persistent weak layer (PWL). The light new snow that is falling on Friday may be enough to cause some more natural activity on the PWL in areas that did not recently slide and have enough wind to develop a heavy windslab load. The new snow and wind may develop a soft surface slab that does not cause the PWL to fail , but may be large enough on their own to injure or bury a person. Avalanches that release on the PWL that is buried down about 70 cm have the potential to be very destructive.

Light new snow is falling across the region today and is expected to continue overnight and into Saturday. This new snow will add to the load above the highly reactive persistent weak layer (PWL), comprising large surface hoar in sheltered areas and a sun crust on solar aspects. This PWL is now buried by about 40-80 cm and resulting avalanches could easily be large enough to bury, injure or kill a person. Snowpack tests on the PWL in the Kootenay Pass area were showing ECTP Moderate down 70 cm. Professionals throughout the region are treating this layer with extreme caution, since it is showing signs of remote triggering and the ability to propagate in low angled terrain. Recent very strong winds have created stiff windslabs that have been cracking and propagating long fractures. The new snow may make it difficult to identify these windslabs especially in openings at treeline and below. In the alpine there may be enough wind to create new windslabs that are softer and probably will not bond well to the old surface. In shallow snowpack areas concerns remain for the mid-December persistent weakness down around 80-100cm and for basal facets. Treeline snowpack depths are approximately 230 cm.