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Avalanche Forecast

Archived

Dec 26th, 2016–Dec 27th, 2016

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
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 and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

South Coast.

A series of storms is ramping up avalanche danger in the South Coast mountains.

Confidence

High -

Weather Forecast

Tuesday: Up to 40cm of new snow is expected to fall by Tuesday morning. Continuing flurries on Tuesday will add approximately 10 cm to this amount. Winds will continue moderate gusting to strong from the southwest. Freezing level rising to 800 metres with alpine temperatures to -1.Wednesday: Isolated flurries delivering a trace of new snow. Winds light gusting to strong from the southwest. Freezing level at 700 metres with alpine temperatures to -3.Thursday: Another storm wave will drop up to 40cm of new snow, intensifying over the day. Winds will be moderate gusting to strong from the south with freezing levels at about 800 metres and alpine temperatures near -1.

Avalanche Summary

Ski cutting in the North Shore mountains on Saturday exposed a weakness about 5cm deep in our previous storm snow. Watch for reactivity at this layer and at the new snow interface as forecast snowfall piles up.

Snowpack Summary

After 5cm of new snow over Sunday night, snow continues to fall on the South Coast mountains. The new snow has fallen on a variable surface that includes pockets of surface hoar and surface facets. Below this, 15 -20cm of dense storm snow overlies a rain crust formed on December 20. A radiation crust that formed on December 19 can be found roughly 30cm deep on solar aspects. These upper layers cap 40cm of well settled storm snow from the series of storms early last week. The storm snow seems to have a good bond to the layers below, where surface hoar and facets have begun to show signs of rounding. An old rain crust buried on December 3 is reported to be down 150-180cm in the North Shore mountains. This layer is well bonded to overlying snow and no stability concerns exist below this layer.

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.