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Archived

Avalanche Forecast

Jan 11th, 2014–Jan 12th, 2014
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
2: Moderate
The avalanche danger rating below treeline will be moderate
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
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
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 Coast.

Weather patterns are divided across the the region: a clearing trend is forecast the north and continued precipitation is expected in the south. Forecast avalanche danger ratings most accurately reflect conditions in areas where snowfall continues.

Confidence

Poor - Forecast snowfall amounts are uncertain

Weather Forecast

The north of the region will see a clearing trend over the next couple of days while moderate snowfall will continue until Monday in the Coquihalla.Tonight and Sunday: Snow tapering off tonight, periods of snow sunday with locally higher amounts in the south of the region / Winds strong to extreme westerly / Freezing level 1100mMonday: Moderate snowfall in the south, dry in the north / Winds moderate to strong westerly / Freezing rising through the day up to 2000mTuesday: Cloudy / Winds moderate to strong southwesterly / Freezing continue to rise as high as 2500m.

Avalanche Summary

Natural and human triggered avalanche activity up to size 2.5 was report to have intensified Friday although these avalanche were a result of developing to storm slabs. Earlier in the week a deep slab avalanche was triggered by a snow cat at Whistler Blackcomb. This avalanche highlights the potential for large and deep avalanches in many areas on the South Coast. As heavy loading continues through the day expect more large deep avalanches.

Snowpack Summary

Saturday's storm clobbered the region with another 60-80 cm of snow. Around 80 -100cm of new snow now overlies a variety of old surfaces which may include surface hoar in sheltered terrain, wind-pressed snow in exposed areas, or a crust on previously sun-exposed slopes. Sustained moderate S-SW winds have loaded in exposed lee terrain and cross-loaded features. In the north of the region, the recent storm snow is sitting on a weak layer of buried surface hoar which formed in early December. Facets from early December's cold snap are a fairly common feature of the snowpack in this part of the region. In some areas, these facets may have formed around a buried crust. In shallow snowpack areas, the facets may exist at ground level. This storms heavy loading will provide the first test of these deep weakness.These deep persistent weak layers do not seem to be as prevalent in the south where the early season snowpack was deeper and was not as affected by early December's cold temperatures.Snowpack depths at treeline range from 170-250 cm in the south of the region, and from 90- 150 cm in the north of the region.

Avalanche Problems

Storm Slabs

Storm slabs will continue to develop with the ongoing snowfall on in the south of the region. In all areas watch for large and reactive wind slabs in exposed north and east facing terrain at and above treeline.
The new snow will require several days to settle and stabilize.>Avoid avalanche terrain during periods of heavy loading from new snow and wind.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1 - 4

Deep Persistent Slabs

Week layers exist deep in the snow pack, particularity in the north of the region.    The "wait 48 hours and you're good" Coastal mantra does not apply as these conditions are likely to persist for some time.
Be aware of the potential for full depth avalanches due to deeply buried weak layers.>Minimize exposure to overhead avalanche terrain, large avalanches may reach run out zones.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 3 - 6