Avalanche Forecast

Issued: Mar 14th, 2012 10:51AM

The alpine rating is extreme, the treeline rating is high, and the below treeline rating is high. Known problems include Storm Slabs, Wind Slabs and Persistent Slabs.

swerner, Avalanche Canada

Sea To Sky.

Avalanche conditions in the alpine are EXTREME. Avoid avalanche terrain.

Summary

Confidence

Good

Weather Forecast

Unsettled, stormy weather conditions continue through the forecast period. Overnight Wednesday: Snow amounts 15-30 cm. Ridgetop winds strong from the SW. Alpine temperatures near -10. Thursday: Snow amounts 20-40 cm. Ridegtop winds strong from the SW. Freezing levels 1200-1400 m. Friday: Light-moderate snow amounts. Strong SW winds. Freezing levels falling to 600m. Saturday: Flurries. Possible sunny breaks, and freezing levels falling to valley bottom.

Avalanche Summary

On Tuesday a natural avalanche cycle occurred up to size 3 on N-NE aspects. Cornices reached their threshold and triggered slopes up to size 2.5 below. On Monday, a skier was partially buried and two others escaped a size 2 slab on an east aspect at 1500m, which failed on a crust. Natural and skier-remote triggered avalanches to size 3 were also observed on a variety of aspects and elevations, some failing on the mid-February weakness. Crowns were up to 150cm deep. Every day of the last week, avalanches have been triggered either naturally, remotely or accidentally by backcountry travelers. With forecast heavy snow amounts, and strong winds, natural avalanche activity will continue. Thursday may be a good day to hunker down, or tear up your local ski resort!

Snowpack Summary

Stormy conditions continue! Over 1m of storm snow has fallen, accompanied by strong SW winds. Storm slabs and wind slabs continue to build. Cornices are large, some reaching threshold and triggering the slopes below. For the most part, the new storm snow is right side up (lower density snow on top) and easy to moderate shears exist within the upper meter. The additional weight of new storm and wind slabs may step down and trigger a deep weakness, formed in mid-February. On Monday, reports of avalanches failingon this layer naturally and with a remote trigger started coming in. Recent test results on this layer produced hard sudden planar results down 120cm in the snowpack (DTH24 SP dwn 120cm on FC/RG 0.5). Very large avalanches are possible, which could be remote-triggered, triggered mid-slope, and/or propagate into low-angled terrain.

Problems

Storm Slabs

Storm slabs are building ever deeper with successive weather systems and are failing under their own weight. They are also overloading persistent weak layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely - Certain

Expected Size

1 - 6

Wind Slabs

Wind slabs lurk below ridges, behind terrain features and in gullies. Strong winds may create slabs unusually low on the slope or in openings below treeline.

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

Elevations: All elevations.

Likelihood

Very Likely - Certain

Expected Size

1 - 6

Persistent Slabs

Persistent weaknesses, now about 1.5m deep, demand respect. The potential for remote triggering, step down avalanches, and wide propagations makes this persistent slab problem particularly intimidating and tricky to manage.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

4 - 8

Valid until: Mar 15th, 2012 9:00AM