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Avalanche Forecast

Archived

Apr 14th, 2014–Apr 15th, 2014

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
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 has been produced using very limited field data. If you've been out in the mountains we'd love to hear about what you've seen. Observations can be sent to [email protected]

Confidence

Fair - Due to the number of field observations

Weather Forecast

Tuesday: Light to locally moderate snowfall / Light to moderate southwest winds / Freezing level at 1000mWednesday: Mix of sun and cloud / Light to moderate southwest winds / Freezing level at 1250mThursday: Moderate to locally heavy snowfall / Moderate to strong southwest winds / Freezing level at 1250m

Avalanche Summary

Although recent observations have been extremely limited, a solar induced natural avalanche cycle to size 3 occurred over the weekend. Loose wet and slab avalanches were noted in this cycle with most activity occurring in steep terrain. Of note, a size 4 deep persistent avalanche occurred in the far north of the region. It released initially within the recent storm snow and stepped down to basal facets. Solar induced activity is expected to taper-off with a possible shift to wind slab activity with forecast weather.

Snowpack Summary

Last week's storm brought 90+ cm or more to coastal regions forming thick storm slabs on leeward features. Warmer temperatures have helped to settle the recent snow, although the storm snow may continue to be touchy where it overlies surface hoar, crusts and/or facets buried at the beginning of April. Sun exposed slopes and lower elevation terrain has seen a daily melt-freeze cycle, and many slopes below treeline are likely isothermal. Large cornices have formed and loom over slopes below.The early February crust/facet layer is down 150 - 240 cm. Triggering this destructive layer will become unlikely with forecast cooling.

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.