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Avalanche Forecast

Archived

Jan 9th, 2014–Jan 10th, 2014

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

South Coast.

Southern parts of the region could see more snow on Thursday night and Friday. Danger ratings reflect higher snowfall amounts. Be sure to make keen local observations. 

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Synopsis: A strong frontal system will reach the South Coast late on Friday and spread heavy to very heavy precipitation, strong winds, and briefly rising freezing levels into Saturday.Friday: Heavy snow developing late in the day 10-15 cm. Very strong SW winds. The freezing level should be around 1000 m during the day, but could peak at close to 1500 m during the storm. Saturday: Continued very heavy snow in the morning, easing through the day 10-15 cm in the north and 20-30 cm in the south. Winds are very strong from the SW but should ease to moderate from the W-NW later in the day. The freezing level rebounds to around 1000 m. Sunday: Moderate snowfall as another weaker frontal system slides in. The freezing level should be around 500 m.

Avalanche Summary

A size 2 deep persistent slab avalanche was reported on Blackcomb Mountain on January 8. This slide was accidentally triggered by a snowcat and released on facets near the ground. Check out Waynn Flann's blog for photos and more information. Two size 2 slab avalanches (human triggered and natural) were observed in Marriott Basin in the Duffey Lake area last weekend. No injuries were reported. The avalanches occurred around 2100m on south-facing terrain. Both were thought to have ran on a crust/facet interface. Check out our Incident Report Database for more details. These incidents highlight the potential for large, full depth avalanches with additional loading heading into the weekend.

Snowpack Summary

Around 10-20 cm of new snow 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. Recent moderate S-SW winds have produced new dense wind slabs in exposed lee terrain and cross-loaded features. In the north of the region, recent storm snow is sitting on a weak layer of buried surface hoar which formed in early December. Facets from December's cold snap also seem fairly widespread in this part of the region. In some areas, these facets may co-exist with a crust. In shallow snowpack areas, the facets may exist at ground level. These persistent weaknesses will likely wake-up with new snow forecast heading into the weekend.Snowpack depths at treeline range from 140-190 cm in the South of the region, and from 80- 130 cm in the North of the region.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.