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Avalanche Forecast

Archived

Dec 29th, 2014–Dec 30th, 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 possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

South Columbia.

Avalanche danger is expected to remain at Considerable during the forecast cold and clear weather for the end of the year.

Confidence

Fair

Weather Forecast

Clear and cold overnight with alpine temperatures dropping to about -25 and moderate Northeast winds. Winds becoming moderate Northwest during the day on Tuesday and alpine temperatures rising up to about -14 under clear skies. Cold and clear with light Westerly winds on Wednesday. Increasing cloud on Thursday with a chance of light snow in the afternoon.

Avalanche Summary

Skiers triggered avalanches up to size 2.0 and remotely triggered avalanches up to size 1.5 that released 30-60 cm down on the mid-December crust/surface hoar weak layer.  Explosives control released avalanches up to size 1.5 on the same persistent weak layer. The persistent slab problem is expected to continue for the forecast period.

Snowpack Summary

There is 10-20 cm of light dry snow that has been transported by Northerly winds into pockets of windsalb in the alpine and at treeline. Below the new snow is the recent storm slab that is 40-90 cm thick and is sitting on a persistent weak layer of crust and surface hoar. The crust extends up to about 2100 metres and seems to be the most reactive at treeline or in the upper below treeline elevations where the surface hoar was well preserved. Fractures have been propagating long distances on this layer and have allowed for remote triggering from adjacent terrain. Deeper in the snowpack there is a hard rain crust from November that may have a weak layer of facets at the interface. This November crust has not been reactive, but continues to be a concern for triggering in shallow snowpack areas.

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.