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Avalanche Forecast

Archived

Dec 25th, 2016–Dec 26th, 2016

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

Watch for winds adding snow to existing slabs on Monday in advance of the storm.

Confidence

Moderate -

Weather Forecast

Monday: Flurries beginning late in the day delivering 5-10cm of new snow. Winds moderate from the southwest. Freezing level to valley bottom with alpine temperatures near -9.Tuesday: Continuing snowfall bringing 10-20cm of new snow, with greater depths in the south of the region. Winds moderate gusting to strong from the southwest. Freezing level rising to 800 metres with alpine temperatures around -7.Wednesday: Mostly cloudy with lingering isolated flurries and a trace of new snow. Winds moderate gusting to strong from the west. Freezing levels just above valley bottom and alpine temperatures to -8.

Avalanche Summary

Explosives control in the north and south of the region on Saturday produced several size 1-2 avalanches with crown depths up to 15cm. Most size 1 results were running as loose dry avalanches. Friday's observations included a natural size 1 avalanche releasing above the December 18 storm snow interface in steep northwest-facing alpine terrain.

Snowpack Summary

10-15cm of new snow over Thursday and Friday may lie above a sun crust on solar aspects in some parts of the region. Where it exists and has been tested, this interface has produced easy sudden collapse results. The new snow brought storm snow totals to 30-60cm since snowfall began at the beginning of last week and loaded leeward features with wind slabs under moderate to strong winds. The storm snow buried old wind slabs, facets and surface hoar. The interface at this layer continues to produce easy to moderate results in snowpack tests. A widespread crust that was buried in November is now 80-100cm deep in the snowpack. Recent tests show variable results with this persistent weakness. Some show results as hard and resistant and others show a sudden character, suggesting it may be likely to propagate if triggered from thin, rocky 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.