Avalanche Forecast

Issued: Mar 14th, 2012 10:54AM

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

Jlammers, Avalanche Canada

Cariboos.

The next major storm is expected to start Wednesday night. If you're sick of seeing red, read the forecaster blog.

Summary

Confidence

Fair - Track of incoming weather is uncertain on Saturday

Weather Forecast

Thursday: moderate to heavy snowfall starting Wednesday evening and continuing through Thursday night - strong southwest winds - freezing level @ 1300m Friday: light snowfall - moderate southwest winds - freezing level @ 800m Saturday: light snowfall - light and variable winds - freezing level @ 1200m

Avalanche Summary

Recent avalanche observations have been fairly limited due to inclement weather. Having said that, evidence of a widespread natural cycle to size 3.5 was observed on Wednesday. I expect ongoing natural avalanche activity with forecast weather on Thursday.

Snowpack Summary

Recent snowfall amounts since the weekend have been quite variable throughout the region. Generally speaking, ongoing moderate daily amounts and moderate to strong southwest winds have contributed to reactive wind and storm slab development. About 160cm below the surface lie buried weak surfaces that formed early February. These include a widespread surface hoar instability that, depending on aspect an elevation, may exist in combination with facets or crusts. These persistent weak layers have been reactive all week and remain a concern at all elevations. The weight of new snow, near-surface avalanches, sleds, and skiers may easily trigger these deeper weaknesses creating unexpectedly large and destructive avalanches.Large cornices have also formed and could act as triggers for slopes below.

Problems

Persistent Slabs

Persistent weaknesses are buried upwards of 150cm below the surface. Surprisingly large and destructive avalanches could be triggered naturally by the weight of additional snowfall, or by the energy of a person/sled.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

3 - 7

Wind Slabs

Forecast snow and strong winds will continued to form reactive wind slabs on lee features. Large cornices may also act as a trigger on slopes below.

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

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 5

Storm Slabs

With ongoing snowfall, storm slabs will form on all aspects and elevations. Surprisingly large, destructive avalanches will occur if storm slabs step-down to a persistent weak layer buried below.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 5

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