Avalanche Forecast

Issued: Dec 14th, 2022 4:00PM

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

Avalanche Canada lbaker, Avalanche Canada

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We now have two concerning persistent weak layers within our snowpack.

Be aware that if triggered, avalanches may step down to deeper layers resulting in large, destructive avalanches. Use extra caution at treeline where weak layers are more prominent and be prepared to back off quickly if you find signs of instability like whumpfing and shooting cracks.

Summary

Confidence

Moderate

Avalanche Summary

On Tuesday in the northern Monashees, a vehicle remote-triggered a size 2.5 persistent slab avalanche on the mid-November layer. Explosives control produced several size 3 and a size 3.5 persistent slab avalanches.

On Monday, a pair of size 2 human-triggered avalanches were reported in the RMR backcountry. These included a skier accidental and a skier remote from 50 m away on the mid-November layer.

Several natural storm slab avalanches were reported, up to size 2, every day this week. Several natural persistent slab avalanches, up to size 3, were also reported. These larger avalanches may have been triggered by solar warming in the afternoons and released or 'stepped down' from smaller avalanches onto deeper instabilities.

Friday

Snowpack Summary

Snowpack depths are highly variable and range from 90cm at treeline to 200cm in the alpine in wind-affected locations.

Surface: 5 - 8mm surface hoar has formed in sheltered areas on the surface of the snowpack. A sun crust is found on steep solar slopes above 2000m. Northerly winds are creating wind slabs in lees and cross-loading features at higher elevations.

Upper-pack: A 40 - 50 cm soft slab overlies a weak layer of 5 mm surface hoar in sheltered and shaded terrain and a sun crust on sunny south-facing slopes.

Mid-pack: Buried 60 to 90cm deep, is a persistent weak layer of surface hoar, crust, and faceted crystals. This layer has been most reactive at treeline between 1700-2200 m, but it was also observed as low as 1450 m and on all aspects.

Lower-pack: Below the mid-November layer is a generally weak, faceted snowpack.

Weather Summary

Wednesday Night

Partly cloudy skies. Northerly ridge wind 20 km/h gusting to 40 km/hr. Alpine temperatures, high of -10. Freezing levels valley bottom.

Thursday

Partly cloudy skies. Northerly ridge winds 20-30 km/h gusting to 40 km/hr. Alpine temperatures, high of -8. Freezing levels valley bottom.

Friday

Partly cloudy skies. Isolated flurries Friday evening in the northern Selkirks, trace accumulation. Northwesterly ridge winds 30 - 40 km/h, gusting to 60 km/h in the Monashees. Possible alpine inversion, temperatures reach a high of -6. Freezing levels valley bottom.

Saturday

Cloudy skies. Light flurries, 2 cm accumulation. Northeasterly ridge winds 30 km/h.  Alpine temperatures, high of -9. Freezing levels valley bottom.

Saturday

 

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be aware of the potential for large, destructive avalanches due to the presence of deeply buried weak layers.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • Minimize exposure during periods of heavy loading from new snow and wind.

Problems

Persistent Slabs

An icon showing Persistent Slabs

There are now two persistent weak layers within the snowpack.

A 30 - 50 cm soft slab sits above a weak layer of 5 mm surface hoar on shaded aspects and crust on steep solar aspects. As northerly winds build wind slabs, adding additional load to the weak layer, we may see another avalanche cycle on this layer.

A second weak layer of surface hoar and facets from mid-November is buried 60 to 90cm in the region. This layer continues to catch professionals and recreationists off guard with numerous large human-triggered avalanches.

Read our featured blog to learn more about how to manage a persistent slab problem when traveling in the backcountry.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 3

Valid until: Dec 15th, 2022 4:00PM