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Avalanche Forecast

Archived

Jan 10th, 2021–Jan 11th, 2021

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

Regions

South Coast Inland.

A storm is forecast to impact the region Sunday night into Monday, with the most snow forecast for the south of the region. New slabs will form and it will load buried weak layers in the north of the region.

Confidence

Moderate - Forecast precipitation (either snow or rain) amounts are uncertain.

Weather Forecast

SUNDAY NIGHT: Cloudy with snowfall, accumulation 5 to 15 cm with the most in the south of the region, 40 km/h southwest wind, alpine temperature -4 C.

MONDAY: Cloudy with snowfall, accumulation 10 to 20 cm, 30 km/h southwest wind, alpine temperature -4 C.

TUESDAY: Cloudy with snowfall, accumulation 5 to 15 cm, 30 km/h south wind, alpine temperature -2 C.

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

Avalanche Summary

Two large avalanches were observed near Duffey Lake on Saturday, described here and here. It is suspected that both avalanches were triggered naturally and on the weak layers described in the snowpack summary. Also, a notable skier-triggered avalanche occurred near Whistler, not far from this region (see the Sea to Sky bulletin for more info).

Snowpack Summary

New storm and wind slabs will form during Sunday night into Monday's storm. The storm is expected to drop around 10 to 30 cm of snow, with the most in the west of the region. The storm will come with strong southwest wind so wind slabs are expected at higher elevations. In sheltered areas, this snow may overlie surface hoar. 

A melt-freeze crust from early December is found around 80 to 180 cm deep in the snowpack. This crust may have surface hoar or sugary faceted grains sitting above it. This persistent weak layer is most prevalent in the north (e.g., Duffey Lake, Hurley).

Terrain and Travel

  • Watch for fresh storm slabs building throughout the day.
  • Be careful as you transition into wind affected terrain.
  • Be aware of the potential for large avalanches due to the presence of buried weak layers.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.