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Avalanche Forecast

Dec 10th, 2012–Dec 11th, 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
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
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: South Columbia.

Confidence

Fair - Intensity of incoming weather is uncertain on Tuesday

Weather Forecast

Overnight and Tuesday: A warm front is moving across the region tonight and a trailing cold front should move through the region in the morning. Expect 15-20 mm by early morning and another 10-15 mm by noon. Strong Westerly winds are forecast during the storm that will ease to moderate with the passing of the cold front. Alpine temperatures should be -9.0 and the freezing level may rise to 900 metres during the storm.Wednesday: There is a weak ridge between systems that should bring very light precipitation, light Westerly winds and temperatures down to -10.0 in the alpine.Thursday: The next frontal system is looking weak at this time. Expect light precipitation and SW winds. Check back tomorrow for an update.

Avalanche Summary

Some very soft slabs were released with explosives control up to size 1.5 and heavy sluffing reported from ski cutting.

Snowpack Summary

The wind may have already started to transport the light surface snow. If not, there should be wind effect by morning, and a lot of snow available for transport into wind slabs. There is widespread sluffing in the new snow in steep unsupported terrain, but no reports of slab avalanche failures in the storm snow. The late November surface hoar is now buried more than a metre deep and close to 150 cms in some of the snowier areas. This layer has mostly been found between 1700-2000 metres in elevation. There have not been any new reports of avalanches sliding on this layer. The early November rain crust is deeply buried. There was one report of a size 3.0 avalanche that released naturally on this layer in the southern Selkirks. I think we need to keep this problem on the front page through another storm cycle, and see how it reacts to more loading and rapid temperature changes.

Avalanche Problems

Storm Slabs

Forecast strong Westerly winds are expected to develop thick wind slabs. Heavy sluffing may be experienced in sheltered terrain.
Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>The new snow will require several days to settle and stabilize.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 5

Persistent Slabs

The weak layer is buried down about 100 cms and should get an additional load added from wind transported snow. Wind slabs above may trigger this deeper layer in unsupported terrain. Elevations between 1600-2100 metres are the most suspect.
Avoid open slopes and convex rolls where buried surface hoar may be preserved.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 2 - 6

Deep Persistent Slabs

The early November rain crust is deeply buried. This layer appears to be very drainage dependant, and there have only been a few avalanches reported across the region. Releases on this layer will be very large and destructive.
Be aware of the potential for full depth avalanches due to deeply buried weak layers.>

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

Elevations: Alpine.

Likelihood: Unlikely

Expected Size: 4 - 7