Avalanche Forecast

Issued: Jan 19th, 2015 8:37AM

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

Avalanche Canada jlammers, Avalanche Canada

Touchy conditions are expected to continue, especially at higher elevations. Check out the most recent Forecaster Blog for more details on the current conditions. http://www.avalanche.ca/blogs/VLsBsCgAACYAJdfM/mid-jan-sh

Summary

Confidence

Fair - Wind effect is extremely variable

Weather Forecast

Expect generally cloudy skies with occasional sunny breaks on Tuesday and Wednesday as a dry weak ridge develops over the southern half of the province. By Thursday it looks like the ridge may break-down somewhat allowing for moist pacific system to enter the region from the northwest. If this happens, accumulations will likely be light. Winds should remain light to moderate from the west-northwest. Freezing levels will hover around 800m on Tuesday and Wednesday, and then rise to about 1000m on Thursday.

Avalanche Summary

Because of stormy conditions throughout the weekend, avalanche observations were quite limited. That said, numerous natural storm slab avalanches to size 2 were noted. Some storm slab avalanches were also triggered remotely from distances of up to 30m. In the north of the region on Sunday, a large avalanche was reported to have failed in alpine terrain and ran all the way to valley bottom. In the height of the storm I'm sure there was more destructive activity in alpine terrain where winds were stronger. Due to the persistent nature of the current instability, I expect continued human triggered slab avalanche activity within the recent storm snow.

Snowpack Summary

Between 30 and 50cm of new snow has fallen since Friday night, and has been distributed by strong winds into deeper, more cohesive deposits in higher wind-exposed terrain. The new snow overlies widespread 10-30mm surface hoar and a sun crust on steep sun-exposed slopes. I would expect continued touchy conditions, especially in areas where the recent snowfall exists as a cohesive slab.The problematic mid-December surface hoar/crust layer is typically down 90-130cm below the surface.. The reactivity of this persistent weak layer appears to be quite variable but still has the potential for large, destructive avalanches in some areas. The layer appears to be the most reactive in the south of the region at and below treeline. In these locations the surface hoar is more likely to sit directly above a hard crust.

Problems

Storm Slabs

An icon showing Storm Slabs
Snow and wind over the weekend has added size and reactivity to a developing storm slab. Prolonged reactivity is expected due to underlying weak crystals.
The new snow will require several days to settle and stabilize.>Use ridges or ribs to avoid pockets of wind loaded snow.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Although less likely to trigger, avalanches failing on deep persistent weak layers formed in December would be highly destructive in nature. Possible triggers include a surface avalanche in motion.
Use caution on open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Jan 20th, 2015 2:00PM