Avalanche Forecast

Moderate - Uncertainty is due to the limited number of field observations.

TUESDAY NIGHT - Clearing and cooling / northwest wind, 20-40 km/h / alpine low temperature near -9 / freezing level valley bottom

WEDNESDAY - Cloudy with sunny breaks / northeast wind, 10-20 km/h / alpine high temperature near -6 / freezing level valley bottom

THURSDAY - Mostly sunny / east-northeast wind, 10-20 km/h / alpine high temperature near -8 / freezing level valley bottom

FRIDAY - Sunny / northeast wind, 10-30 km/h / alpine high temperature near -10 / freezing level valley bottom

On Monday in the Ningunsaw area, explosives triggered an impressive size 4 persistent slab avalanche which took out mature forest, and another five size 2.5-3 persistent slab avalanches in adjacent terrain. Additionally, wind slabs were reactive to skier traffic and explosives triggered wind slab avalanches to size 2.

A handful of wind slab avalanches to size 2 failing naturally were observed Sunday. Avalanches to size 2 were reported on more southwesterly to southeasterly aspects above 1200 m. Skiers easily cut size 1 pockets in loaded terrain.

A natural avalanche cycle occurred Thursday into Friday with storm and wind slab avalanches to size 2, with poor visibility likely limiting alpine observations. The strong winds reached below treelline elevations - reports of numerous wind slab avalanches observed in steep terrain with crowns 20-30 cm deep and up to 150 m wide. Check out this MIN report here of a large persistent slab avalanche that likely occurred during the Thursday-Friday natural cycle.

Just over a week ago, explosives triggered a few size 2 persistent slab avalanches near the southern boundary of the region (Jan 10). And explosive control work near Ningunsaw (just outside the region, on Jan 9) produced several wind slabs to size 2.5 and one size 3 deep persistent slab failing on weak facets near the base of the snowpack. As we continue to track this persistent weak layer, these are a reminder of the "low probability; high consequence" scenario that persistent slab problems often create.

Another 5-15 cm fresh accumulating around the region Tuesday adds to the recent incremental snow. Gusty and variable winds have impacted loose snow and developed slabs in exposed areas. Warm temperatures have produced a crust up to 800 m and higher on solar aspects.

A layer of surface hoar maybe be found under recent storm snow (now down 20-50 cm) around treeline. In the south of the region, another weak layer of surface hoar that was buried around the New Year has been reported down 50-70 cm in sheltered areas.

The lower snowpack has two crusts with potentially weak, faceted snow around them. Reports from the Smithers area suggest the upper crust is 70-140 cm below the surface and has shown signs of being possible to trigger from shallow areas. The deeper crust is near the bottom of the snowpack and is most likely to trigger from steep, rocky slopes, with a shallow or thin to thick snowpack. Recent avalanches failing on this basal layer were reported from the Ningunsaw area.

• Recent wind has varied in direction so watch for wind slabs on all aspects.
• Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
• Be alert to conditions that change with elevation and wind exposure.
• Be especially cautious near rock outcroppings, on steep convexities and anywhere the snowpack feels thinner than average.
• Be aware of the potential for large avalanches due to the presence of a persistent slab.