Check for wind loading before committing to big lines. Slabs are still reactive to human triggers and recent winds from the north and south may have loaded unexpected features.
Storm snow has been redistributed by southwest winds into deeper, reactive slabs in wind loaded features. Take care when moving through wind affected terrain and higher elevations. Expect fresh slabs to keep building over the day as moderate winds continue.
A layer of weak facets (sugary snow) can be found down 80-150 cm near a crust layer that formed in early December. Although this persistent weak layer hasn't recently shown reactivity in this area, it is possible to trigger avalanches on this layer, especially at treeline elevations.
The best strategy with a persistent avalanche problem is conservative terrain management - avoid likely trigger spots such as steep convex slopes, and areas where the snowpack tapers rapidly from thick to thin. Learn more about this problem here in a recent forecaster blog.
The arctic grip continues. Temperature decrease over the week with light snowfall possible each day.
SATURDAY NIGHT: Up to 5cm overnight. Easterly winds.
SUNDAY: Light snowfall over the day, up to 5cm expected. Light to moderate easterly winds. Alpine highs of -20.
MONDAY: Clearing skies with increasing westerly winds. Alpine high of -20.
TUESDAY: Partly cloudy with isolated flurries. Alpine high of -22. Light westerly winds.
The heavy snowfall this week produced a natural slab cycle to size 3 throughout the region on Wednesday and Thursday. Human triggered slabs were also observed to size 1 in wind loaded features.
A notable size 1 remote wind slab was remotely triggered on a north aspect below treeline. Riders felt a settlement while in the runout, and this triggered the slab on a steep piece of terrain on an adjacent slope. While this avalanche was small, it does indicate the reactivity of the persistent weak layers in the lower snowpack and the potential for fractures to travel over a distance. This avalanche problem is challenging to forecast and is best managed by conservative terrain management.
If head into the mountains, please submit your findings and photos through a Mountain Information Network report.
Up to 40cm of fresh storm snow has accumulated this week. In the alpine and exposed treeline elevations it has been redistributed into deeper deposits in wind loaded features by wind. In the southern parts of the region, southwest winds have been dominant. In the northern part, southwest winds came in with the snow and are now followed by a northerly blast, redistributing snow into unusual loading patterns.
At lower elevations the settling storm snow may sit over a weak surface hoar layer, which is creating slabs that are reactive to human triggers. The surface hoar is most likely to be found on sheltered slopes at treeline and below.
The crust formed by the early December rain event sits 100-150cm deep and is found up to 2200m in the North Columbia's. In most terrain the snow above is well bonded to the crust. In areas where the crust is buried deeper than one meter, it has begun to decompose and shows limited reactivity.
However in some areas, weak faceted grains have been observed above - creating a weak interface that is still reactive to human triggers. This is most common at treeline elevations where the crust is thinner.
