Avalanche Forecast

Issued: Apr 19th, 2013 10:24AM

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 Loose Wet.

jlammers, Avalanche Canada

South Coast.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

Light snowfall is forecast for Saturday with greater amounts possible in the Coquihalla/ Allison Pass areas. Moderate west winds are expected with freezing levels at about 1800m. On Sunday and Monday the region should see generally clear skies, light north winds and freezing levels at about 1500m.

Avalanche Summary

In recent days, numerous rider triggered and isolated remote/sympathetic events have been reported in high (2300-2700m) north and northeast facing slopes up to size 2.5, all associated with preserved surface hoar. Much of the reported activity on buried surface hoar seems to be occurring in the north of the region in the Duffey Lake/ Birkenhead areas, through the Hurley and up towards Bralorne/Goldbridge.

Snowpack Summary

Generally light daily snow accumulations have been observed in the last few days, and soft wind slabs likely exist on lee terrain. About 30-60 cm below the surface lies the April 5th layers. On solar aspects, the layer is a strong melt-freeze crust, with some faceting observed above and below. On Northwest to Northeast aspects above about 2300m, 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 5th interface lingers as a persistent problem, especially in the north of the region. Touchy surface hoar on NW-NE aspects above about 2300m and (to a lesser extent) facets on a crust on previously sun-exposed slopes.

Be aware of the potential for large avalanches due to the presence of buried surface hoar.>Be alert to conditions that change with elevation.>Carefully evaluate big terrain features by digging and testing on adjacent, safe slopes.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 5

Wind Slabs

New softslabs will continue to form in lee of features with forecast snow and moderate westerly winds. Greater snowfall amounts are expected in the south of the region.

Avoid freshly wind loaded features.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Loose Wet

Loose wet avalanche activity will be likely, especially if the sun comes out on Saturday.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

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

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Apr 20th, 2013 2:00PM