Southwest winds and light snowfall will continue to create reactive slabs in wind effected terrain features. Buried weak layers still show unpredictable triggering - avoid steep unsupported slopes and areas where the snowpack rapidly thins.
Take care when moving through wind affected terrain and higher elevations - storm snow has been redistributed by southwest winds into deeper, reactive slabs in wind loaded features. Expect fresh slabs to keep building over the day as moderate winds continue.
A layer of weak facets (sugary snow) can be found down 70-150 cm near a thick crust layer that formed in early December. Even though it is a deeply buried, it is still possible to trigger avalanches on this persistent weak 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.
Arctic air pushes south into the interior, mixing with a low pressure system off the coast of Vancouver. Temperatures will steadily drop but expect a daily refresh of low density snow through to Boxing Day.
FRIDAY NIGHT: Up to 5cm overnight. Light to moderate southwest winds. Alpine low of -10.
SATURDAY: Cloudy with light snowfall, 2-5cm over the day and another 5-10cm overnight. Accumulations will favour the south - Kokanee Glacier area. Moderate gusting strong southerly winds. Alpine high of -8.
SUNDAY: Up to 5cm over the day, and another 5cm possible overnight with easing winds, shifting west. Alpine highs of -15.
MONDAY: Clearing skies with increasing westerly winds. Alpine high of -20.
Yesterday a natural slab cycle was observed to size 2 at all elevations throughout the region. Natural activity occured in the storm snow, and on the recently buried surface hoar.
Slabs were also very easily triggered by skiers and riders, observed to size 2 on all aspects. A sympathetic size 1 was observed in a below treeline feature, failing on the surface hoar indicating very sensitive avalanche conditions.
Another notable result was a skier triggered persistent slab avalanche, failing on the early December crust/facet interface that has been lurking in the snowpack with unpredictable results. The slab was 80cm deep, and occurred on a southwest facing unsupported treeline slope. This indicates that this layer is still a concern for human triggering - conservative terrain choices are the best defence against this tricky problem.
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 southwest winds.
At lower elevations the settling storm snow may sit over a weak surface hoar layer, which is creating reactive conditions 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 70-150cm deep and is found up to 2400m in the South Columbia's. In most terrain the snow above is well bonded to the crust. Additionally, 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.
