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Avalanche Forecast

Dec 20th, 2011–Dec 21st, 2011
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
1: Low
The avalanche danger rating at treeline will be low
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
1: Low
The avalanche danger rating at treeline will be low
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Sea To Sky.

Confidence

Good - -1

Weather Forecast

Wednesday: Mainly sunny, with freezing levels in valley bottoms and moderate northwesterly winds. Thursday: Increasing clouds with a chance of flurries in the evening. Freezing levels rising as high as 1500m, and moderate southerly winds. Friday: 5-10cm of snow, with freezing levels around 1200m, and moderate southwesterly winds.

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 wind slabs are bonding poorly to the variable but predominately crust snow surface from last weekend's warm, wet, and windy weather. Recent compression tests on a wind-loaded treeline slope produced easy to moderate sudden collapse results down 65cm on surface hoar overlying faceted snow. 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.

Avalanche Problems

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.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3