There have been a couple of large avalanches failing deep in the snowpack. See Forecast Details for more info.
Summary
Confidence
Fair - Due to variable snowpack conditions on Friday
Weather Forecast
Overnight and Friday: A weak trough of low pressure is moving in from the coast. Expect light winds and light precipitation overnight to bring about 5mm to most parts of the region. Western parts of the region may see up to 15 mm that should fall as snow above 800 metres.Saturday: Light westerly winds are expected to clock to the Northwest and increase to moderate as an upper ridge builds over the Eastern Pacific. Alpine temperatures should dip down to about -12.0 with broken skies becoming clear overnight.Sunday: Clear and cold in the morning, temperatures down to -16.0 in the alpine. This should be short lived as the next Pacific warm front approaches from the coast.
Avalanche Summary
Professionals working in the Southern Selkirks experienced a very large settlement that propagated a fracture about one kilometre (1000 metres) on Wednesday. The fracture was reported to have traveled through some forest and across several pieces of avalanche terrain without releasing an avalanche. The loud whumph was the result of a failure on the deeply buried early November rain crust. After this experience, some explosive control from a helicopter resulted in a size 3.0 avalanche releasing on the buried crust that was approximately 200 cms below the surface. There was also natural and explosives controlled avalanches on the November 28th surface hoar layer that is buried down 40-70 cms.
Snowpack Summary
There are wind slabs of varying thickness and stiffness in the alpine and at treeline that were formed earlier in the week from very strong winds and warm temperatures during the storm. There is a surface hoar layer (November 28th) that is buried between 40-70 cms as the slab above has become more consolidated. This layer appears to be mostly between 1600-2000 metres in elevation, and may be very reactive in areas that experienced valley fog last week when it formed. The big unknown is the deep persistent weak layer (DPWL) of early November rain crust. This layer formed in early November when a warm rain event extended well up into the alpine and than froze into an ice layer. This layer is found where there was enough snow on the ground at the time of this event to become saturated and then freeze. Large scree slopes, areas where snow was still on the ground from last winter, and some smooth glaciers are the most suspect locations.
triley,
Avalanche Canada
