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Avalanche Forecast

Archived

Apr 17th, 2014–Apr 18th, 2014

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Northwest Coastal.

This bulletin was created using very limited field data. If you are out in the mountains, please send your observations to [email protected]

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

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.