Avalanche Forecast

Issued: Jan 29th, 2016 8:08AM

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

jlammers, Avalanche Canada

South Coast.

Destructive persistent weak layers should still be on your radar if you're heading to the north of the region.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Expect 5-15cm 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

On Thursday, persistent and storm slab avalanches to size 3.5 were observed on a variety of aspects and elevations. They occurred in response to heavy storm loading from rain and snow. The mid-January surface hoar was the suspected culprit in many of these avalanches. Of note was a size 4 slab avalanche in Steep Creek in the Duffey Lake area. Thanks to the individual who submitted this great observation through the Mountain Information Network. Moving forward, cooling will likely put a cap on persistent slab avalanche activity, except on higher elevation slopes in the north of the region where reactivity is expected to persist. Forecast wind and snow will spark a new round of wind slab activity in high elevation lee terrain over 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 60 and 130 cm below the surface. The combination of heavy storm loading and warm temperatures has likely flushed out this weak layer in many areas. I would still exercise caution on higher elevation slopes in the north of the region where continued reactivity at this destructive interface is likely to persist. New snow and wind on Friday night and Saturday will form new wind slabs in high elevation lee terrain.

Problems

Persistent Slabs

In many 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, Treeline.

Likelihood

Possible

Expected Size

3 - 6

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

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

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