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Avalanche Forecast

Archived

Jan 1st, 2021–Jan 2nd, 2021

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Northwest Coastal.

Waves of storms are impacting the region. An avalanche cycle is expected to occur this weekend. Travel in avalanche terrain is not recommended.

Confidence

High -

Weather Forecast

FRIDAY NIGHT: Cloudy with snowfall, accumulation 10 to 20 cm, 60 to 80 km/h southwest wind, alpine temperature -3 C, freezing level 900 m.

SATURDAY: Cloudy with snowfall, accumulation 15 to 25 cm, 80 km/h southwest wind, alpine temperature -3 C, freezing level 1000 m dropping to 700 m.

SUNDAY: Cloudy with snowfall, accumulation 20 to 30 cm, 40 to 60 km/h southwest wind, alpine temperature -6 C.

MONDAY: Cloudy with snowfall, accumulation 5 to 10 cm, 40 to 60 km/h south wind, alpine temperature -6 C.

Avalanche Summary

We received reports of the new snow being very reactive to human traffic on Friday. A natural avalanche cycle is expected to occur at some point during this stormy period, once sufficient snow loads the buried weak layers described in the snowpack summary. Avalanches are very likely to be triggered naturally and/or by riders this weekend.

Snowpack Summary

A hefty storm is impacting the region this weekend. 20 to 30 cm of snow has accumulated so far and upwards of 60 cm more snow may accumulate by the end of the weekend. Storm slabs are expected to be rapidly forming. The snow is falling with strong southwest wind, which is likely also rapidly forming wind slabs in exposed terrain. 

All of this snow is loading two layers of weak and feathery surface hoar, found between 30 and 70 cm deep. The surface hoar was reported as being widespread prior to burial and the upper layer may sit on a melt-freeze crust from warm air on Boxing Day and/or from sunny skies.

Around 100 to 200 cm deep, a hard melt-freeze crust from early December may have weak and sugary faceted grains around it. These weak layers are likely the culprit of avalanche activity last weekend in the Nass Valley, Sterling, and Beaupre riding areas.

The early-November melt-freeze crust is over 200 cm deep and may have faceted grains above it in parts of the region, particularly in the north. The last reported avalanche activity was near Ningunsaw on December 11.

Terrain and Travel

  • Travel in alpine terrain is not recommended.
  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
  • Avoid exposure to overhead avalanche terrain, avalanches may run surprisingly far.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.