North Columbia

Ongoing light snowfall and moderate winds Sunday night should continue to build wind slabs and cornices at higher elevations. Use extra caution on solar aspects and around cornices if the sun comes out Monday afternoon.

Moderate -

3-6 cm of new snow is forecast for Sunday overnight with moderate southwest wind in the alpine. Another 5-10 cm is expected on Monday with light alpine wind and freezing levels reaching around 1500 m in the afternoon. Tuesday is expected to be mainly cloudy with sunny breaks in the morning and light snow in the afternoon. Alpine wind is forecast to be light to moderate from the southwest and freezing levels are expected to reach around 1500 m. Similar unsettled conditions are currently forecast for Wednesday with sunny breaks and light snowfall both possible.

On Saturday, a natural cornice release triggered a size 2 storm slab on a north aspect at 2600 m and a size 1.5 wind slab was observed on a north aspect at 2500 m. Skiers and snowmobiles triggered several size 1 storm slabs and wind slabs, mainly on northwest through northeast aspects above 2000 m. Most of these recent slab avalanches were 20-40 cm thick but one was 50 cm thick and released on the mid-March crust. On Friday, small storm slabs were reactive to skier traffic on convex and wind loaded northerly aspects. The last avalanches to step down to deeper layers were on Thursday when explosives triggered cornices which pulled slabs 100-200 cm thick. On Monday, the recent storm snow is expected to be reactive at higher elevations, especially in wind loaded terrain and on steep convex features. Cornices are large and may become weak with daytime warming or during stormy periods. We are in a low probability, high consequence scenario for persistent slab avalanches failing on deep buried weak layers. Click here for more details. Click here for photos the avalanche cycle last week.

20-50 cm of snow has now accumulated over the past week which overlies a rain crust below around 2000 m or a sun crust on solar aspects at higher elevations. Alpine wind has recently been strong mainly from south through west directions and has loaded leeward slopes in exposed terrain at treeline and in the alpine. Large cornices are also reported in the alpine. At lower elevations, there may be multiple crust layers in the upper snowpack which are now generally well bonded and stable. At higher elevations, the February weak layers are down 120-150 cm and woke up during last week's storm with many avalanches stepping down. The deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack and a few avalanches and cornice falls also stepped down to these layers last week resulting in some very large full depth avalanches.