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Avalanche Forecast

Mar 20th, 2012–Mar 21st, 2012
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: South Rockies.

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.

Avalanche Problems

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

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

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