Avalanche Forecast

Issued: Jan 29th, 2016 7:47AM

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

jlammers, Avalanche Canada

Sea To Sky.

Watch for new wind slab formation throughout the weekend.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Expect 10-20cm of new snow to fall between Friday night and Saturday. An additional 5cm may fall on Sunday, while isolated flurries and sunny breaks are forecast for Monday. Winds on Saturday will be strong from the southwest, and then drop to light and northwesterly for Sunday and Monday. Freezing levels should hover between 500-700m for the entire forecast period.

Avalanche Summary

Backcountry avalanche observations were extremely limited during this week's storm; however, wet slab, loose wet and storm slab avalanches to size 3.5 were noted. I'm sure the storm also triggered a few persistent slab avalanches. We'll know more about that as operators are able to get out and make observations over the next few days. Moving forward, there will likely be a shift to wind slab activity with wind and snow forecast for the weekend.

Snowpack Summary

On Wednesday night and Thursday morning, heavy snowfall and strong winds continued to form deep and dense storm slabs in high elevation terrain and cause substantial cornice growth. The snow line fluctuated a great deal during the storm which dropped around 80mm of precipitation throughout the region. At treeline and below, heavy rain saturated the snowpack. With forecast cooling, slopes at these elevation bands may now be sporting a hard crust. Where it still exists, the mid-January surface hoar layer is between 100 and 180 cm below the surface. The combination of heavy storm loading and warm temperatures has likely flushed out this weak layer in most areas. In the wake of the storm, there will still be some uncertainty regarding the reactivity and distribution of this destructive persistent avalanche problem, especially at high elevations in the north of the region where continued reactivity at this interface has been observed. New snow and wind on Friday night and Saturday will form new wind slabs in high elevation lee terrain.

Problems

Wind Slabs

New snow and wind over the next few days will form new wind slabs in high elevation lee terrain. Watch for triggering in gullies and behind ridge crests.

Avoid freshly wind loaded features.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

Aspects: North, North East, East, South East, South, South West.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Cornices

Recent stormy weather has encouraged widespread cornice growth. Cornice falls can be destructive by themselves, but can also be a trigger for surprisingly large avalanches on the slope below.

Give cornices a wide berth when travelling on or below ridges.>

Aspects: North, North East, East, South East.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

In most areas, buried persistent weaknesses have been destroyed by recent wet and stormy weather. I'd still be cautious in high elevation terrain (particularly in the north of the region) as the snowpack adjusts to the weight of the new snow.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Jan 30th, 2016 2:00PM