Avalanche Forecast

Arctic air continues to push south, keeping the Columbia's well below seasonal temperatures. An active low pressure system approaches on Wednesday night.

SUNDAY NIGHT: 5cm possible overnight with winds easing and shifting winds.

MONDAY: Cloudy skies with moderate westerly winds. Alpine high of -20. 

TUESDAY: Partly cloudy with isolated flurries. Alpine high of -22. Moderate westerly winds. 

WEDNESDAY: Strong westerly winds increase over the day. Alpine high of -22. A mix of sun and cloud. 

A size 1 skier triggered wind slab was reported yesterday, running on a recently buried freezing rain crust that is present in the south of the region. 

The heavy snowfall this week produced a natural slab cycle to size 2 throughout the region on Wednesday and Thursday 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 60cm 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. 

• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
• Be aware of the potential for large avalanches due to the presence of a persistent slab.
• Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.