Avalanche Forecast

Issued: Jan 9th, 2014 7:36AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is low. Known problems include Storm Slabs and Persistent Slabs.

Peter, Avalanche Canada

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.

Summary

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 slabs continue to build. Watch for touchy wind slabs to form in exposed north and east facing terrain at and above treeline.

Be alert to conditions that change with elevation.>Use ridges or ribs to avoid pockets of wind loaded snow.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

The likelihood of triggering persistent weaknesses in the mid-pack and near the ground is increasing. It's likely we will see a number of very large, full-depth avalanches by Saturday.

Use caution in shallow snowpack areas where triggering is more likely.>Use caution on open slopes and convex rolls at treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Jan 10th, 2014 2:00PM