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Avalanche Forecast

Archived

Nov 29th, 2021–Nov 30th, 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 avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Coast Inland.

Another atmospheric river storm will bring lots of precipitation and rising freezing levels. As a result, expect to see a widespread avalanche cycle with the potential for large, full-path avalanches. Avoid all avalanche terrain.

Please respect all restrictions on BC highways. 

Confidence

High - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.

Weather Forecast

The third of a series of atmospheric river winds its way down the BC coast. By Tuesday morning all coastal ranges will be in the throes of another torrential rain situation.  

Monday night: Flurries; 10-15 cm. Strong to extreme southwest winds. Alpine low temperatures -3 C with freezing levels at 1500 metres.

Tuesday: Periods of snow mixed with rain; 15-30 cm and even more overnight. Extreme southwest winds. Alpine high temperatures -1 C with freezing levels at 1700 metres then peaking overnight at 2200 metres in the north of the region and 3000 m in the south of the region.

Wednesday: Snow, heavy at times mixed with rain; 10-20 cm. Moderate to extreme southwest winds.Alpine high temperatures +2 C with freezing levels at 2000 metres.

Thursday: Mainly cloudy with scattered flurries; 5 cm. Moderate southwest winds. Alpine high temperatures -7 C with freezing levels at 800 metres.

Avalanche Summary

Large avalanches sliding on recently buried surface hoar and deeper buried crusts have been observed in the region as well as in the neighboring Sea to Sky. With another atmospheric river storm affecting the area Tuesday and Wednesday, expect to see a widespread avalanche cycle with the potential for large, full-path avalanches.

Snowpack Summary

Recent snowfalls and strong southerly winds continue to develop storm slabs in the alpine and at treeline with ticker accumulations in leeward features. All this new snow sit over a layer of surface hoar down 70-100 cm and a deeper crust / facets combo that produced large avalanches during Saturday's storm. Heavy loading and warming coming with this intense storm will likely produce more avalanche activity on these layers.

Average snowpack depths in the alpine are now 130-180 cm. Below treeline, depths of 30-50 cm have been reported around 500 m, decreasing dramatically with elevation, and still below threshold for avalanching in many areas. Early season hazards such as rocks, stumps, and creeks are a concern below the alpine.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.
  • Be aware of the potential for large, deep avalanches to run full path or even longer.

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.