Avalanche Forecast

Issued: Mar 17th, 2012 10:35AM

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 Persistent Slabs.

pgoddard, Avalanche Canada

South Rockies.

Avalanche danger could spike to HIGH in any areas receiving direct sunshine.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

Sunday: Scattered convective snow showers. Freezing level rising to around 1500m. Light winds. Monday: A mix of sun and cloud. Tuesday: Cloud, turning to snow by late morning. Wind increasing from the south-west.

Avalanche Summary

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. On Saturday, snowpack tests in the southern Elk Valley showed a couple of shears in the top 20cm of storm snow. A rain crust is buried about 1m down. Two surface hoar layers, buried in February and now 1-2m deep, exhibited sudden planar results, which have been repeated in a number of locations. This means they 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

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

Possible - Likely

Expected Size

1 - 6

Storm Slabs

Recent storm snow may release naturally with the first blast of direct sun. 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

Possible - Likely

Expected Size

1 - 6

Persistent Slabs

Persistent weak layers, now buried 1-2m deep, still have the potential to produce large and dangerous avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 8

Valid until: Mar 18th, 2012 9:00AM