Avalanche Forecast

Issued: Dec 19th, 2011 9:15AM

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

Avalanche Canada ccampbell, Avalanche Canada

Summary

Confidence

Good - -1

Weather Forecast

Tuesday: Light snowfall with 5-10cm of accumulation, freezing levels dropping to valley bottoms and moderate westerly winds. Wednesday: Mostly clear and dry with freezing levels in valley bottoms and light southeasterly winds. Thursday: Increasing cloud with flurries possible late in the day. Freezing levels remaining in valley bottoms.

Avalanche Summary

Recent observations include several artificially triggered Size 1, and one Size 2, wind slab avalanches from steep lee and cross-loaded alpine slopes. In the Diamond head area of Garibaldi Park, a natural Size 2.5 slab avalanche was observed on Sunday on a large steep wind-affected slope. Several natural loose snow avalanches up to Size 2 occurred in response to the rain/warming event on Saturday and sun-exposure on Sunday. Deep persistent slab avalanche activity on any basal layers is highly unlikely at this time.

Snowpack Summary

In exposed treeline and alpine areas touchy thin wind slabs are bonding poorly to a crust that formed after Saturday's warm temperatures and rain, and cornices are growing. Recent compression tests on a wind-loaded alpine slope produced easy to moderate sudden collapse results down 65cm presumably on last week's surface facets and/or surface hoar. The mid and lower snowpack are generally well settled and strong, but facets may be lurking at base of the snowpack in shallow alpine areas.

Problems

Wind Slabs

An icon showing Wind Slabs
Fresh wind slabs are lurking below ridge crests, behind terrain features and in cross-loaded gullies.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Dec 20th, 2011 8:00AM

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