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Avalanche Forecast

Archived

Jan 19th, 2014–Jan 20th, 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 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 unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Kootenay Boundary.

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

Synopsis: A strong ridge of high pressure over BC and western Alberta is doing a good job of blocking Pacific moisture from the region. An inversion will see temperatures higher in the alpine than at treeline.Overnight: Nil precipitation. Winds light to moderate from the west, freezing level at valley bottom.Monday: Nil precipitation. Winds light at ridge tops, freezing level in the alpine to 1300m.Tuesday: Nil precipitation. Winds light at ridge tops, freezing level in the alpine to 1400m.Wednesday: Nil precipitation. Winds light at ridge tops, freezing level in the alpine to 1400m.

Avalanche Summary

Recent explosive controls reported results in storm snow only. Sluffing in steep terrain, snowballing and pinwheel activity on steep solar aspects.

Snowpack Summary

Wind continues to redistribute surface snow throughout the region. The snowpack varies widely, but appears to be deeper in the north and east. Basal facets continue to be a concern where wind slabs and storm slabs have added load above these weak layers. The forecast very warm alpine temperatures may result in periods of rapid warming of the wind and storm slabs above weak layers. Strong solar radiation may cause moist or wet loose snow avalanches or cornice falls in the alpine resulting in large additional loads above deeply buried weak layers. Surface hoar has been reported forming on protected north and east slopes along with facetting of the surface and storm slab in protected locations.

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.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.