Avalanche Forecast

Issued: Jan 17th, 2021 4:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Wind Slabs, Persistent Slabs and Loose Wet.

Avalanche Canada dsaly, Avalanche Canada

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Another pulse of moisture will try to splash over from the coast late Monday. Expect avalanche hazard to rise with incoming wind, flurries, and rising temperatures.

Summary

Confidence

Moderate - Uncertainty is due to the limited number of field observations. Uncertainty is due to difficult to forecast freezing levels.

Weather Forecast

SUNDAY NIGHT- Cloudy with isolated flurries / southwest wind, 40-60 km/h / alpine high temperature near -3 / freezing level valley bottom

MONDAY - Mainly cloudy / increasing southwest wind, 30-60 km/h / alpine high temperature near -1 / freezing level rising up to 1200 m

TUESDAY - Snow starting late Monday, 5-15 cm / west wind, 50-90 km/h / alpine high temperature near -2 / freezing level 1100 m

WEDNESDAY - Cloudy with sunny breaks / northeast wind, 20-30 km/h / alpine high temperature near -8 / freezing level valley bottom

Avalanche Summary

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.

On 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. 

Explosives triggered a few size 2 persistent slab avalanches reported near the southern boundary of the region on Sunday. And last Saturday, explosive control work near Ningunsaw (just outside the region) 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.

Snowpack Summary

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. 

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.

Terrain and Travel

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Keep your guard up at lower elevations. Wind slab formation has been extensive.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Be especially cautious near rock outcroppings, on steep convexities and anywhere the snowpack feels thinner than average.

Problems

Wind Slabs

An icon showing Wind Slabs

Winds have impacted loose snow at all elevations, including exposed terrain below treeline.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent 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.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 3

Loose Wet

An icon showing Loose Wet

Rising freezing levels may produce a wet-loose hazard at lower elevations. Avoid steep slopes and terrain traps at low elevations where the snow is wet.

Aspects: All aspects.

Elevations: Below Treeline.

Likelihood

Possible

Expected Size

1 - 1.5

Valid until: Jan 18th, 2021 4:00PM