Avalanche Forecast
Issued: Jan 11th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
kdevine,
Avalanche Canada
Use caution as you transition into wind exposed terrain, new snow combined with southwest winds have promoted wind slab development at upper elevations.
Summary
Confidence
Moderate - Uncertainty is due to the limited number of field observations.
Weather Forecast
MONDAY NIGHT - Flurries, 5-10 cm / southwest wind 60-80 km/h / alpine low temperature near -6 /Â
TUESDAY - Flurries, 5-10 cm / southwest wind 20-40 km/h / alpine high temperature near -10Â
WEDNESDAY - Mainly cloudy with a few flurries / southwest wind 40-50 km/h / alpine high temperature near -10
THURSDAY - Mainly cloudy / southeast wind 30-60 km/h / alpine high temperature near -6
Avalanche Summary
Wind slabs are expected to be reactive to human triggers on Tuesday, especially at upper elevations.
There were a few explosives triggered size 2 avalanches reported near the southern boundary of the region on Sunday.
On 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. Another reminder of the "low probability; high consequence" scenario that persistent slab problems often create.
Snowpack Summary
5-10 cm of fresh snow and strong to extreme southwest winds have likely formed reactive wind slabs in exposed terrain in the alpine and at treeline. These new wind slabs may sit on a weak layer of surface hoar that was recently buried at at treeline and below treeline.Â
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 70-100 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
- 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.
- 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
Strong winds may form fresh wind slabs throughout the day on lee features at treeline and above.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
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
Expected Size
Valid until: Jan 12th, 2021 4:00PM
