Avalanche Forecast

Issued: Apr 17th, 2013 10:19AM

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

mpeter, Avalanche Canada

South Coast.

Summary

Confidence

Poor - Intensity of incoming weather is uncertain

Weather Forecast

Thursday: Cloudy skies with temperatures reaching -2 and freezing levels climbing to 1900m. Expect light westerly winds and a chance of isolated flurries with limited accumulations.Friday: Expect continued unsettled skies with more isolated flurries, temperatures around -1 and light westerly winds. Freezing levels may again reach 1900m.Saturday: Clouds linger with more intermittent flurries. Alpine temperatures should be around -3 with continuing light west-southwest winds.

Avalanche Summary

Numerous rider triggered and isolated remote and sympathetic events have been reported in high (2400-2700m) north and northeast facing slopes up to size 2.5, all associated with preserved surface hoar.

Snowpack Summary

North and Northeast aspects above 2000m continue to hold dry snow; otherwise, the surface condition is crusts. The carrying strength of the crusts varies depending on aspect and elevation as well as proximity to rocks, etc.... Generally speaking, the crusts have been going moist in the afternoon and then refreezing at night in all but the lowest terrain. The recent storm snow has settled into a cohesive slab between 30-60cm deep. At the interface of this storm snow lies the April 05 layers. On solar aspects, the layer is a strong melt-freeze crust, with some faceting observed above and below. Reactivity on this layer has been inconsistent, with occasional sudden results and some whumphing. On North and Northeast aspects above 2350m, this interface may be preserved surface hoar (up to 15mm). Where the surface hoar is present we have reports of sudden results in stability tests and have seen rider triggered, sympathetic and remote events up to size 2.5. Professional operators express consistent concern for triggering this layer.Cornices are huge and will continue to grow with the forecasted precipitation.

Problems

Persistent Slabs

The April 05 interface lingers as a persistent problem. Surface hoar on N/NE aspects above 2350m and (to a lesser extent) facets on a crust on solar aspects

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Dig down to find and test weak layers before committing to a line.>

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 5

Wind Slabs

New softslabs will form in lee features with the forecasted new snow. Older windslabs, now buried, may still be reactive.

Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Cornices

New snow and wind will add mass to existing cornices. Cornices can act as a large trigger to deeper weaknesses.

Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 6

Valid until: Apr 18th, 2013 2:00PM