Avalanche Forecast

Issued: Feb 11th, 2016 8:14AM

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

triley, Avalanche Canada

Northwest Coastal.

A series of new storms are expected to develop new storm slabs at higher elevations. Deeply buried persistent weak layers continue to be a concern for large avalanches.

Summary

Confidence

Moderate - Freezing levels are uncertain

Weather Forecast

Strong southeast winds overnight with light precipitation and freezing levels around 800 metres. Moderate southwest winds with 10-15 mm of precipitation on Friday and freezing levels around 800-1000 metres. Light precipitation and moderate southerly winds on Saturday with freezing levels between 700-1000 metres. Moderate to heavy precipitation on Sunday with moderate southwest winds and rising freezing levels. Heavy precipitation is forecast for Monday.

Avalanche Summary

Explosives control on Thursday resulted in a size 2.5 slab avalanche that released on the persistent weak layer in the north of the region in the Ningunsaw area. On Wednesday, several loose wet slides were reported from the Shames backcountry that were visible in the Geronimo bowl. On Tuesday explosives control in the Bear Pass highway corridor produced slab avalanches in the alpine up to size 4.0 with wide fracture propagations. Reports of natural activity during the recent storm of slab avalanches up to size 4.0 releasing in the storm snow or on the deeply buried persistent weak layer from early January.

Snowpack Summary

Observations have been sparse due to poor flying and travel conditions, as well as poor visibility. In the Shames backcountry on Wednesday there was no crust at 1300 metres ( the highest point the observer reached), and we suspect the crust is only above 1500 metres. There was 50 cm of recent storm snow, with the top 25 cm being rain soaked. This moist and wet storm snow was sitting on the old crust from the previous warm storm at the end of January. Compression tests resulted in moderate shears within the storm snow and on the old crust. The January 9th surface hoar/facet layer is down 70-200 cm across the region and remains a concern for commercial operations. There continues to be a lot of uncertainty regarding the reactivity and distribution of this destructive persistent avalanche problem; however, warm temperatures have increased the likelihood of triggering these layers where they still exist. A very conservative approach to mountain travel is still required.

Problems

Persistent Slabs

The deeply buried persistent weak layer of surface hoar was reactive during the last wet storm. It has not cooled off much, and more warm wet weather is forecast. Uncertainty with this layer requires conservative terrain selection.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

Storm Slabs

New storm slabs are expected to develop in the alpine, and possibly at treeline if the freezing level drops more than forecast.

Be cautious as you transition into wind affected terrain.>Be alert to conditions that change with elevation.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 3

Loose Wet

Moist or wet snow may continue to release naturally or with light additional loads until the freezing levels drop.

Be cautious of wet sluffing in steep terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Feb 12th, 2016 2:00PM