Avalanche Forecast

Issued: Mar 30th, 2012 11:19AM

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

mpeter, Avalanche Canada

Kootenay Boundary.

If more snow falls than forecasted (>15cm), the danger may be HIGH. Be locally aware of conditions.

Summary

Confidence

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

Weather Forecast

Saturday: A system south of the border will send moderate precipitation into the region, accompanied by moderate southwesterlies. 15cm is possible. Freezing levels could climb to 1500m. Sunday / Monday: A series of lows will push precipitation into the region with continued southerly flow and freezing levels reaching 1200m.

Avalanche Summary

Natural, explosive and human triggered avalanches have been reported up to size 2.0 failing 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.There was one sympathetic triggered avalanche that release on the early February weakness 150cm deep.

Snowpack Summary

30-50cm 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. The bond between the new snow and this interface is weak, especially where the surface hoar is present. At lower elevations (1600m and below), the high freezing levels have made the new snow heavy and moist. The deep, persistent early February surface hoar lingers in the snowpack giving sudden results in testing. Concern remains with heavy triggers and rapid loading.

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

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

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

Valid until: Mar 31st, 2012 9:00AM