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Avalanche Forecast

Archived

Dec 24th, 2016–Dec 25th, 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 unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Kootenay Boundary.

Watch for signs of instability as the sun pokes out on Sunday and snowfall begins on Monday.

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Monday

Weather Forecast

Sunday: Cloudy with sunny periods and no new snow. Winds light from the west. Freezing level at valley bottom with alpine temperatures to -11.Monday: Flurries with up to 10cm of new snow. Winds moderate from the southwest. Freezing level at valley bottom with alpine temperatures to -10.Tuesday: Flurries with up to 10cm of new snow. Winds moderate to strong from the southwest. Freezing level rising to 800 metres and alpine temperatures to -8.

Avalanche Summary

Explosives control in the south of the region on Saturday produced several size 2 avalanches with crown depths up to 20cm. Friday's observations included a natural size 1 avalanche releasing storm snow above the December 18 interface in steep northwest-facing alpine terrain. Observations from earlier in the week include wind slab avalanches triggered from explosives control running on the same storm/old snow interface to size 2 at treeline and above.

Snowpack Summary

10-15cm of new snow over Thursday and Friday has brought storm snow totals to 30-60cm since snowfall began at the beginning of the week. The storm snow has buried old wind slabs, facets and surface hoar. There is some uncertainty regarding how the new snow is bonding to old surfaces which formed during last week's cold clear period. Moderate to strong winds have loaded leeward features with wind slabs. 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.