Archived

Avalanche Forecast

Mar 28th, 2012–Mar 29th, 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

3: Considerable

The avalanche danger rating below treeline will be considerable

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: Kootenay Boundary.

If the snowfall amounts are higher than forecast, expect HIGH danger.

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Thursday: Expect unsettled conditions, with flurries becoming heavy at times. 20cm are possible with winds turning westerly and becoming gusty. Freezing levels could reach 1600m. Friday / Saturday: Another stormy day with continuing westerly winds and a possible 10cm. Freezing levels may again reach 1500m. Expect a drying trend overnight, with Saturday being mixed sun and cloud.

Avalanche Summary

Natural, explosive and human triggered avalanches have been reported up to size 2.0, with all failures on the March 26 interface. At lower elevations (where the surface is moist) these are running as loose events and at higher elevations the new snow is propagating as a slab.

Snowpack Summary

Above 2000m, 20-40cm of new snow now overlies the March 26 interface. This has been accompanied by consistently moderate and at times gusty southwesterly winds forming windslabs in lee locations. Cornices loom, and will continue to grow with this weather pattern. The March 26 interface is a crust on all aspects except true north treeline and alpine, where small surface hoar (5mm) is present in sheltered places. At lower elevations, the surface snow has had less recovery and the upper snowpack is predominantly moist. The deep, persistent early February surface hoar lingers in the snowpack giving sudden results in testing. Concern remains with heavy triggers.

Avalanche Problems

Wind Slabs

The increased wind and new snow are forming windslabs in lee zones at ridgecrest. These overlie a slick melt freeze crust in most locations and surface hoar on North aspects. A small windslab event could step down to the deep, persistent weakness.

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

Elevations: Alpine, Treeline.

Likelihood: Likely - Very Likely

Expected Size: 1 - 4

Storm Slabs

The new snow is bonding poorly to the March 26 interface. At lower elevations, expect moist sluffing, while higher up (drier snow) the storm slab is more cohesive. A small storm slab event (or sluff) could step down to the deep weaknesses.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely - Very Likely

Expected Size: 1 - 4

Cornices

Cornices are very large and will grow under the current conditions. There is potential for triggering deep persistent slabs on underlying slopes.

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

Elevations: Alpine.

Likelihood: Possible - Likely

Expected Size: 2 - 7