Human triggered avalanches are likely this weekend as fresh snow sits above a fragile weak layer.
A weak surface hoar layer is buried 50-70 cm below the surface. New snow or the weight of a rider could easily trigger avalanches on this layer.
Thick storm slabs formed on Friday and will remain reactive over the weekend, especially in steep and wind loaded terrain.
FRIDAY NIGHT: Cold front crosses the region, 15 cm of new snow, strong wind from the southwest, freezing level drops to valley bottom with alpine temperatures dropping to -10 C.
SATURDAY: Flurries with accumulations of 10-15 cm in southeast parts of the region and 5 cm in northwest parts of the region, moderate to strong wind from the west, alpine high temperatures around -6 C.
SUNDAY: Mostly cloudy with scattered flurries, 5-10 cm of new snow, strong wind from the southwest, alpine high temperatures around -4 C.
MONDAY: Mostly cloudy with scattered flurries, 5-10 cm cm of new snow, moderate wind from the south, alpine high temperatures around -6 C.
Reports continue to confirm persistent slab avalanches are easy to trigger. Prior to New Year's, several large avalanches were reported on a buried surface hoar layer (including these MIN reports from the Farm and Pine Pass). Since then this persistent slab has continued to be reactive on even small terrain features like cut banks (see MIN reports from McBride and Silver Sands). With the additional snow from Friday's storm, both storm slab and persistent slab avalanches are a concern this weekend.
A frontal system crossing the region on Friday will deliver 20-40 cm of fresh snow by Saturday afternoon. This will leave a weak layer of feathery surface hoar buried 50-70 cm below the surface. Reports suggest this layer has been reactive in all parts of the region, as numerous avalanches have been reported over the past week. This layer remains at a burial depth where it can easily be triggered by humans.
There are a pair of potential weak layers in the middle of the snowpack, a surface hoar layer and a layer of facets above a relatively thin crust. Both these layers appear to be gaining strength. The lower snowpack contains several crust layers, which could be a concern in shallow areas along the eastern slopes of the region.
