A fast moving pulse of moisture and wind will quickly build reactive storm slabs.
Triggering large avalanches on weaknesses in the lower snowpack remains a possibility. In some areas the concern is weak snow around crusts 70-100 cm deep, while in others it is weak snow near the bottom of the snowpack. Human triggering of these layers are most likely in steep, rocky slopes with a shallow or thin to thick snowpack.
A pulse of moisture could dump up to 25 cm along with strong, gust wind. Expect increasingly reactive slabs to develop.
Freezing levels are expected to spike overnight and drop through Tuesday. Avoid steep slopes and terrain traps at low elevations where snow is wet.
MONDAY NIGHT - Mainly cloudy / Strong southwest wind, gusting upwards of 100 km/h / alpine high temperature near -1 / freezing level rising up to 1200 m
TUESDAY - Snow starting late Monday, 10-20 cm / west wind, 60-90 km/h / alpine high temperature near -2 / freezing level 1100 m and dropping through the day
WEDNESDAY - Cloudy with sunny breaks / northeast wind, 20-30 km/h / alpine high temperature near -8 / freezing level valley bottom
THURSDAY - Cloudy with sunny breaks / southeast wind, 10-20 km/h / alpine high temperature near -8 / freezing level valley bottom
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.
Last Tuesday, a previous avalanche cycle occurred in the south of the region as slab avalanches up to size 2 failed naturally in wind loaded terrain.
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.
Ongoing flurries and incremental loading dropped 15-25 cm fresh snow in recent days. 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 weak layer of surface hoar, maybe be found under recent storm snow (now down 20-50 cm) at treeline and below 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.
