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Avalanche Forecast

Archived

Jan 9th, 2014–Jan 10th, 2014

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

Regions

Kootenay Boundary.

Moderate to heavy precipitation combined with rising temps and high winds will drive the danger ratings for the next few days.

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

Friday: 10 to 15 cm at upper elevations on Friday . Moderate to strong westerly winds for the day. Freezing levels are forecast to rise to 1000 m.Saturday: Increased precipitation, with up to 20 cm as a Pacific frontal system moves through the area. Freezing levels may rise to 1300 meters during the storm with strong SW winds.Sunday: Freezing level returns to 700 M in the wake of the Pacific frontal system, leaving another 10 cm in the forecast area. Strong winds persist.

Avalanche Summary

Surface sluffing only in recent reports.

Snowpack Summary

Moderate to heavy amounts of snow forecast for the weekend with strong SW winds will create wind slabs at tree line and above. Sluffing may occur in steep terrain and could easily run on surface hoar in sheltered alpine areas and below treeline. This surface hoar layer is sitting on a sun crust on S facing aspects in some locations. The persistent weak layers (PWL) are a concern to avalanche professionals as they have been producing sudden planar results and show good propagation potential when tested. The end of November facet/crust or surface hoar layer down 80 cm (or 40 cm where snowpack is very thin) and the depth hoar or basal facetting are the most worrisome layers. Presently, they do not seem reactive to skier triggering but this situation may change with additional loading from the incoming storm, rising temperatures, and strong wind.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.

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.