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Avalanche Forecast

Mar 13th, 2013–Mar 14th, 2013
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
4: High
The avalanche danger rating below treeline will be high
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
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: South Columbia.

High freezing levels, moist snow, and strong winds will result in High Avalanche Danger at all elevations.

Confidence

Fair - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

Overnight and Thursday: The next strong pulse of moisture is forecast for Wednesday night, and is expected to continue during the day on Thursday. 10-20 cms overnight and another 20-30 cms during the day. Warm temperatures are not expected to lower overnight, and freezing levels should remain at about 1600 metres.Friday: The Pacific moisture feed should end by late morning as the Low pressure system tracks Northward up the coast. Temperatures and freezing levels should begin to lower. Chance of some broken skies in the afternoon.Saturday: Continued unsettled weather in the wake of the storm. Poor confidence in weather scenarios for Saturday.

Avalanche Summary

A widespread cycle of natural avalanches up to size 2.0 was reported early in the storm before poor visibility and travel conditions limited observations.

Snowpack Summary

Another pulse of heavy precipitation is forecast to add to the already moist heavy storm slab that is covering a widespread layer of surface hoar (March 10th layer) that developed during the recent clear weather. Strong Westerly winds during the storm have developed thick wind slabs at higher elevations where the snow was drier and easily transported. Sun crusts also developed during the clear weather on solar aspects up to about 1800 metres. Some areas had strong winds before the surface hoar was buried, so the distribution may be specific to sheltered and shaded terrain features. There is still concern for the buried weak layer of surface hoar from February 12th that is now down more than a metre in most places. The forecast new load of snow and wind may overload this deeply buried weak layer in areas that did not slide after the last storm.

Avalanche Problems

Storm Slabs

Another pulse of heavy precipitation and continued warm temperatures is expected to add to the already moist and reactive storm slab. Storm slabs are expected to release naturally or be triggered from adjacent terrain.
Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>The new snow will require several days to settle and stabilize.>Stay well back from cornices.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 2 - 6

Persistent Slabs

A weak layer of buried surface hoar down about 100-150 cm may be triggered by the load of new storm snow and wind.
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

Expected Size: 4 - 7