Avalanche Forecast

Issued: Mar 20th, 2012 10:20AM

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

Avalanche Canada pgoddard, Avalanche Canada

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain

Weather Forecast

Wednesday: A few flurries. Light winds. Freezing level at valley bottom at night and around 1000m in the afternoon.Thursday: Light to moderate snow. Gusty winds. Freezing level is uncertain, but could rise to around 1600m.Friday: A mix of sun and cloud. Freezing level is uncertain, but could rise to around 1700m in the afternoon.

Avalanche Summary

On Tuesday, wind slabs in the size 1-1.5 range were triggered naturally and by skiers at treeline and above on slopes loaded by south-westerly winds. On Sunday, a size 1.5 avalanche released naturally on a north aspect. On Saturday, a recent avalanche was observed on a north aspect in the southern Elk Valley, suspected to have started as a wind slab and ending in moist snow. Evidence of a previous natural cycle was also reported. On Friday, explosives produced size 1-2 avalanches.

Snowpack Summary

Unsettled weather has brought snow and wind through most of the week, creating variable wind slabs and storm slabs. Newly formed 10-20cm thick wind slabs were easy to trigger on Tuesday at treeline and above. A melt-freeze crust buried below recent storm snow exists to 1900m on south aspects and 1700m elsewhere. An older rain crust is buried about 1m down. Two surface hoar layers, buried in February and now 1-2m deep, continue to exhibit sudden planar results, which have been repeated in a number of locations. This means these layers still have the potential to produce widely-propagating, destructive avalanches if triggered. Most likely triggering mechanisms are a person traveling on a thin snowpack area, or a storm slab, wind slab or cornice stepping down. Basal facets may still exist, particularly in shallow snowpack areas with steep, rocky start zones. Cornices have grown large and threaten slopes below.

Problems

Wind Slabs

An icon showing Wind Slabs
Wind slabs can be found behind ridges and terrain breaks. Large cornices also threaten slopes below.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 6

Storm Slabs

An icon showing Storm Slabs
New snow was very touchy on Tuesday and may take time to settle. It's possible for surface avalanches to step down to a weak persistent layer, initiating large destructive avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 6

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Persistent weak layers, now buried 1-2m deep, still have the potential to produce large and dangerous avalanches. They could be triggered by cornice fall, smaller avalanches stepping down, or under the weight of a snowmobile and rider.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

4 - 8

Valid until: Mar 21st, 2012 9:00AM

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