Avalanche Forecast

Issued: Apr 17th, 2014 9:13AM

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

rbuhler, Avalanche Canada

Northwest Coastal.

This bulletin was created using very limited field data. If you are out in the mountains, please send your observations to forecaster@avalanche.ca

Summary

Confidence

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

Weather Forecast

Unsettled conditions are expected for Friday and Saturday morning before the next organized storm system arrives on the north coast Saturday afternoon. Precipitation is expected Saturday night and Sunday but there is some uncertainty regarding amounts and timing.Friday: A mix of sun and cloud, light scattered flurries, freezing level am: 700m pm: 1000m, ridgetop wind: light SW-WSaturday: Light precipitation 2-4mm, freezing level am: 800-1000m pm: 1200-1400m, ridgetop wind: becoming moderate-strong S-SW with storm frontSat. Night: Precipitation 8-12mm, freezing level: 1000m, ridgetop wind: strong S-SWSunday: Precipitation 6-12mm, freezing level am: 1000m pm: 1300m, ridgetop wind: moderate-strong S-SW

Avalanche Summary

On Monday, a slab avalanche size 2.5 was remotely triggered on a North facing alpine slope in the North Eastern part of the region. This slab released on the deep persistent weak layer buried in mid-February. Widespread activity occurred over the weekend caused by warm temperatures and strong solar radiation. Things have typically stabilized over the last few days due to cooler temperatures and lack of sun. Avalanche activity is expected to increase with warmer temperatures, new snowfall, and moderate-strong winds.

Snowpack Summary

New snow may sit on a crust which exists up to around 1400m on solar aspects or on last week's storm snow (90cm+ in areas of the region). Winds slabs are expected to form in lee features from moderate-strong S-SW winds.Recent warmer temperatures have helped to settle the underlying snowpack. In shallower snowpack areas or on steep, unsupported features, the old storm slab may still be reactive to human-triggering. This older storm slab is sitting on a surface hoar, a crust, and/or facets buried at the beginning of April. Large cornices may still be a concern, especially during periods of warming or heavy loading. The early February crust/facet layer is typically down 1.5 to 2.5m. A smaller avalanche or a cornice fall may still have the potential to step down to layer causing very large, destructive avalanches.

Problems

Storm Slabs

New snow is expected to form widespread storm slabs and stiffer wind slabs in leeward features. It may still be possible to trigger the thicker, older storm slab from the last storm, especially on steep unsupported slopes and thinner snowpack areas.

Make observations and assess conditions continually as you travel.>Avoid unsupported slopes.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Deep Persistent Slabs

A deeply buried persistent weak layer still has the potential to produce very large avalanches and could be triggered by heavy triggers such as cornice falls or smaller avalanches stepping-down.

Conditions have improved, but be mindful that deep instabilities are still present.>There is potential for large, deep avalanches due to the presence of buried facets and surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

3 - 7

Valid until: Apr 18th, 2014 2:00PM