Avalanche Forecast

Issued: Mar 8th, 2012 9:32AM

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

swerner, Avalanche Canada

Cariboos.

Summary

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Unstable conditions expected through the weekend. The first front will bring light to moderate snow amounts, accompanied by a strong upper SW flow. The Western ranges may see higher snow amounts, and the second frontal system looks to be a bit punchier. Friday: Snow amounts 15-30 cm. Ridgetop winds moderate-strong from the SW. Treeline temperatures near -8. Freezing levels 1200 m. Saturday: Moderate snow amounts. Ridgetop winds moderate from the SW. Freezing levels 1200-1400 m. Sunday: Snow amounts 5-10 cm by late afternoon, then heavier amounts may extend into the night. Freezing levels falling to 10000 m.

Avalanche Summary

On Wednesday a natural size 3.5 was reported including several size 2.5, that remotely (from afar) triggered low angle slopes. Operators did full explosive testing and reported numerous large avalanches. This could indicate the triggering potential that lies ahead. The persistent weakness is susceptible to new storm slab, wind slab, cornice fall, sled and skier triggers. The scary fact is the size of the avalanches. Even a small avalanche could step down and trigger a persistent weak layer, which in turn will create a large, destructive avalanche. Many rider triggered size 1-2 avalanches have also been reported. Monday/Tuesday the region saw a widespread natural avalanche cycle in response to snow, wind and warming. With more snow and wind in the forecast the avalanche danger will elevate.

Snowpack Summary

The weekend past, 60-100 cm of snow fell. Strong winds and fluctuating temperatures have created storm slabs and wind slabs. Buried below 100-180 cm sit the mid-February persistent weak layers (surface hoar, facets, crusts).These persistent weak layers have remained touchy all week and are a concern at all elevations. They could be triggered by storm slabs, wind slabs, or the additional load of a sled/skier. Avalanches may be unexpectedly large, and destructive. Large cornices have formed, and could act as a potential trigger on the slope below.

Problems

Wind Slabs

Lots of snow available for transport, accompanied by strong winds have created wind slabs, even at treeline elevations. Large cornices may act as a potential trigger on slopes below.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Persistent Slabs

Persistent weaknesses exist in the 170 cm of the snowpack. Surprisingly large avalanches could be triggered naturally by storm snow loading, or by additional weight of a person/sled. Buried persistent weaknesses are tricky to predict.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 7

Storm Slabs

New snow and fluctuating temperatures have formed storm slabs. These overlie the mid-February weak interface. Storm slabs that trigger this interface could create surprisingly large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 5

Valid until: Mar 9th, 2012 8:00AM