Avalanche Forecast

Issued: Mar 21st, 2014 9:38AM

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

bcorrigan, Avalanche Canada

South Coast.

The hazard may go higher than forecast on solar aspects if the sun comes out and the temperature goes higher than expected. Pay careful attention temperatures and cornice hazard.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

Synopsis: A weak ridge of high pressure sits over the forecast area and should block out any major precipitation for the next 2 days.Tonight: Clear periods, no precipitation in the forecast, freezing level around 100 metres, winds light, from the north.Saturday: Cloudy with trace a of precipitation, freezing level around 1300 metres, ridge top winds should be light from the south east.Sunday: Cloudy periods, trace of precipitation in the forecast, freezing level around 1800 metres, light ridge top winds from the south west.Monday: Cloudy with flurries, freezing level around 2000 metres, winds light to moderate from the south.

Avalanche Summary

A few reports of skier controlled and skier accidental avalanches on north aspects from yesterday. Also reports of solar sluffing on steep south aspects. Conditions seem to be improving, but It may be too early to be stepping out to bigger objectives.

Snowpack Summary

Between 30and 50 cm of 7-day storm snowstorm snow has increased the slab sitting on the persistent weak layers. Strong westerly winds continue to form wind slabs on lee slopes. The two persistent weak layers that remain a concern are:The March weak layer. A combination of hard wind-scoured slab surfaces in exposed terrain, facets and/or surface hoar in sheltered and north aspects, and sun crust on steep solar aspects and is generally widespread throughout the forecast region. This layer is now down between 70 and 80cm from the surface.A late January/early February crust/facet/surface hoar combo that is still showing up in snowpack tests with hard shear tests, now down 150 to 250cm from the surface. Recent warming temperatures will be good for bonding above and below this layer, but a sudden increase in load, a cornice failure, or a big rain event could "wake up" this layer and result in large avalanches. There are also basal facets at the bottom of the snowpack from cold clear weather in early December, but for the most part these have not been a concern, however, recently, large avalanches have scoured some avalanche tracks down to the basal facets and even to the ground.

Problems

Storm Slabs

Small, continuous amounts of storm snow have left us with wind slabs at tree line and above. Steep solar aspects may become active when the sun comes out on the recent storm snow. A cornice failure could produce a large destructive avalanche.

Assess start zones carefully and use safe travel techniques.>Be cautious as you transition into wind affected terrain.>Pay attention to overhead hazards like cornices.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Deep Persistent Slabs

The persistent weak layers buried deep in the snowpack were recently reactive with new snow loading. Warming temperatures or a sudden load, ( cornice failure) could wake up this layer.

Be aware of thin areas that may propogate to deeper instabilites.>Be aware of the potential for full depth avalanches due to deeply buried weak layers.>Give cornices a wide berth when travelling on or below ridges.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Mar 22nd, 2014 2:00PM