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Avalanche Forecast

Archived

Jan 8th, 2012–Jan 9th, 2012

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

Regions

Cariboos.

Confidence

Fair - Forecast snowfall amounts are uncertain on Monday

Weather Forecast

20-30 cm is forecast for Sunday and overnight into Monday morning combined with moderate to strong southwest winds and freezing levels around 1200 metres. Another 5-10 cm is forecast for Monday with moderate southwest winds and freezing levels dropping to valley bottoms by evening. Cooler and drier weather with light northwest winds is expected for Tuesday and Wednesday.

Avalanche Summary

No new avalanche activity reported.

Snowpack Summary

Strong southwest winds and moderate to heavy precipitation has begun to build new windslabs in the alpine and at treeline. The recent snowfalls add up to about 60-80 cm of "storm" snow that has been available for wind transport. The warm temperatures and high freezing levels caused the wind transported snow to become a well consolidated slab. There are two rain crusts below 1550 metres. The rain crusts are variable, but they are giving planar results in tests. At treeline the storm snow is reported to be giving sudden planar results down 40 cm, and the surface hoar/crust layer that is down 80cm is also giving sudden planar results. This tells me that the new load of snow that we are expecting may activate these weak layers. The mid-pack is reported to be strong, and I have not heard anyone talk about early season layers deep in the snowpack.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.