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Avalanche Forecast

Dec 15th, 2012–Dec 16th, 2012
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Sea To Sky.

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Synopsis: A strong frontal system is forecast to reach the South Coast late on Sunday bringing heavy snow and strong winds. Conditions should be unsettled in the wake of the system with flurries and occasional sunny breaks. Sunday: Periods of snow, heavier in the evening and overnight. 25-40 cm by Monday morning. Winds increasing to strong from the SW-SE with the arrival of the system. Freezing level around 500 m. Monday: Snow easing to flurries and possible sunny breaks. Around 5 cm. Freezing level remains around 300-500 m. Tuesday: Cloudy with flurries. Freezing level near valley bottom.

Avalanche Summary

Recent activity has been limited to a few small (size 1) soft slab avalanches in immediate lee features and small loose snow avalanches in steep terrain. Observations from early last week included several old size 2-3 avalanches, primarily from northerly aspects in the alpine. These events may have released on a weak layer of surface hoar, now down over a metre deep.

Snowpack Summary

Several potential weaknesses may exist within or under the new storm snow, including one or two surface hoar layers and a sun crust. Recent winds have been stiffening the low density storm snow and forming reactive slabs in exposed lee terrain. Below the recent storm snow weaknesses, the snowpack is well settled and strong. A layer of surface hoar that formed during late November has been found intact or decomposing in some locations down a meter or more. The early November crust/facet combination near the base of the snowpack seems to be dormant, at least in deep snowpack areas where it is buried too deeply by a stiff snowpack to be affected by light triggers on the snow surface.

Avalanche Problems

Storm Slabs

Weaknesses are likely within or below the new storm snow and may be triggered naturally or by the weight of a person or snowmobile.
Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Stick to non-avalanche terrain or small features with limited consequence.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 4

Wind Slabs

Expect to encounter deep and touchy wind slabs below ridge crests, behind terrain features, and in cross-loaded gullies.
Be cautious as you transition into wind affected terrain.>Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>

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

Elevations: Alpine, Treeline.

Likelihood: Very Likely

Expected Size: 2 - 5