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Avalanche Forecast

Archived

Jan 8th, 2018–Jan 9th, 2018

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

Regions

Lizard-Flathead.

Lots of uncertainty in the snowfall forecast for Tuesday and Wednesday. Danger ratings reflect forecast intense snowfall.

Confidence

Low - Forecast snowfall amounts are uncertain

Weather Forecast

TUESDAY: Cloudy with snow. One senior meteorologist is predicting a 'Fernie effect', which could bring up to 50 cm of dry snow in quick order late in the day. Light to moderate winds. Alpine temperature near -6.WEDNESDAY: Light winds. Light snow. Alpine temperature near -10.THURSDAY: Light winds. Moderate snow. Alpine temperature near -10.

Avalanche Summary

Explosives triggered several size 1.5-2.5 storm slabs on Monday morning. Skiers were also triggering loose dry avalanches which were gathering mass and running up to size 2. Reports of persistent slabs being triggered by people, machines and even remotely (from a distance) continue to come in, particularly at and below treeline. Check out the reports on the Mountain Information Network here. On Thursday, a skier-triggered size 2 slab on a north-east aspect at 1975 m near Fernie caught and partially buried four people. Check out the details here. Touchy avalanche conditions will continue as new snow continues to stress weaknesses in the snowpack.

Snowpack Summary

New snow is building storm slabs. Old and new wind slabs and cornices can be found at ridge top. If intense snowfall rates occur, loose snow avalanches are likely to run fast and far. A very touchy weak layer from mid-December (predominantly feathery surface hoar crystals and/or a sun crust) is found down about 40-90 cm. It is most prevalent at and below treeline, and seems particularly volatile between about 1600-1800 m. Deeper in the snowpack, an early season rain crust and sugary facets make up the picture. It is possible that a shallower avalanche could step down to these layers, creating a surprisingly large event.

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.