North Columbia

Avoid large features and convex slopes. New snow and warm temperatures are increasing the avalanche danger, and an unpredictable persistent slab problem has been active the last few days.

Steady moderate snowfall and rising temperatures through the forecast period. Expect heavier snowfall and warmer temperatures in the Monashees.

MONDAY NIGHT: Overcast. 2-5 cm of snow expected. Light southwest wind trending to strong at higher elevations. Treeline temperatures around -7 C.

TUESDAY: Overcast. 5-15 cm of snow expected. Light to moderate southwest wind trending to extreme at higher elevations. Freezing level rising to around 900 m.

WEDNESDAY: Overcast. 5-10 cm of snow expected overnight, with another 10-25 cm through the day. Moderate south wind trending to extreme southwest at higher elevations. Freezing level rising to around 1300 m.

THURSDAY: Overcast. 10-35 cm of snow expected overnight, and a possible trace through the day. Light southwest wind trending to moderate northwest at higher elevations. Freezing level around 1300 m.

On Sunday and Monday, several small, loose dry skier triggered avalanches were reported across the region. Also, west of Revelstoke, explosive avalanche control produced several large loose dry avalanches.

On Saturday, isolated size 1.5 to 2.5 natural and skier triggered windslab avalanches were reported around treeline on various aspects across the region.

The persistent early December crust/facet layer has recently been active in this region. A very large storm slab avalanche (size 3) ran naturally in Mount Revelstoke National Park on Friday afternoon. Up to 3 m of snow buried the highway. This avalanche path rarely affects the road (only once every 5 or 10 years). The avalanche appears to have been caused by a storm slab that stepped down to a deeper, persistent layer.

Also on Friday, a professional operation west of Revelstoke reported a large natural avalanche on this persistent layer in a northwest facing feature at treeline. On Sunday, an operation in the East end of the region reported two large to very large explosive triggered avalanches on this layer on east and northeast aspects near treeline.

Consistent snow and southwest wind has left us with a mix of settling storm snow and windslabs in the upper snowpack. As new snow falls and recent snow settles on top of faceted snow that formed during the colder weather last week, the upper meter of the snowpack may get a bit upside-down and become more likely to avalanche.

We're actively monitoring the early December crust. In shallow spots it's down 90 cm while in wind-loaded terrain features it can be found as deep as 200 cm below the surface. It consists of faceted grains above a bulletproof crust formed by the Atmospheric Rivers of early December. There has been avalanche activity on this crust over the weekend.

• Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
• The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
• Storm slabs in motion may step down to deeper layers resulting in large avalanches.
• The likelihood of deep persistent slab avalanches will increase with each day of warm weather.
• Avoid terrain traps such as gullies and cliffs where the consequence of any avalanche could be serious.