Avalanche Forecast
Regions: Northwest Inland.
Extreme southwesterly winds will form fresh wind slabs in open terrain. Reactive wind slabs may be found much lower on slopes than what is typical.
Confidence
Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system. Forecast precipitation (either snow or rain) amounts are uncertain.
Weather Forecast
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SUNDAY NIGHT: Snow; 5-10 cm. / Extreme, southwest ridgetop wind / alpine low temperature -7 / Freezing level 500 m.
MONDAY: Flurries; 3-5 cm. / Strong, southwest ridgetop wind / alpine high temperature -5 / Freezing level 700 m.
TUESDAY: Flurries; 3-5 cm. / Light, southwest ridgetop wind / alpine high temperature -6 / Freezing level 500 m.
WEDNESDAY: Cloudy with isolated flurries; 0-3 cm. / Moderate, southwest ridgetop wind / alpine high temperature -7 / Freezing level 400 m.
Avalanche Summary
On Saturday, explosive control work near Ningunsaw 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. Another reminder of the "low probability; high consequence" scenario that persistent slab problems often create.
Additional snow and extreme winds are expected to form reactive wind slabs in open terrain.
Snowpack Summary
Strong to extreme winds are forming reactive wind slabs in exposed terrain at treeline and above. In the south of the region, a weak layer of surface hoar has been reported down 50-70 cm. in isolated sheltered areas.
The lower snowpack has two crusts with potentially weak snow around them. Reports from the Smithers area suggest the upper crust is 70-100 cm below the surface and has shown signs of being possible to trigger from shallow areas. The other 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
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
- 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.
Avalanche Problems
Wind Slabs
Extreme winds may form fresh wind slabs throughout the day on lee features at treeline and above. Wind slabs in motion may step-down to deeper weak layers resulting in large avalanches.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 2
Persistent Slabs
Triggering large avalanches on weaknesses in the lower snowpack remains a possibility. In some areas the concern is weak snow around crusts 60 to 90 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 - Possible
Expected Size: 2 - 3