Avalanche Forecast

Issued: Dec 25th, 2016 3:17PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs.

Avalanche Canada cgarritty, Avalanche Canada

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

Summary

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

An icon showing Wind Slabs
Wind slabs will grow in size and reactivity with forecast wind and snow. Potential exists for a wind slab avalanche to trigger deeper weaknesses in the snowpack.
Watch for signs of instability such as whumpfing, or cracking. Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Be cautious as you transition into wind affected terrain.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 26th, 2016 2:00PM

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