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Avalanche Forecast

Archived

Mar 16th, 2014–Mar 17th, 2014

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

Sea To Sky.

Confidence

Fair - Due to the number and quality of field observations

Weather Forecast

Synopsis: A low pressure system in the Gulf of Alaska will feed moisture onto the coast and into the interior for the next 4 or 5 days.Tonight: Cloudy with flurries, trace of precipitation, freezing level at valley bottom, light ridge top winds occasionally gusting to moderate.Monday: Sunny periods with a few clouds, no precipitation in the forecast, freezing level around 800 metres, winds from the west, to 40 Km/hr.Tuesday: Cloudy with flurries, possible 5 to 10 cm of precipitation,, freezing level around 1000 metres winds from the south west, light occasionally gusting to moderate.Wednesday: Sunny with cloudy periods and isolated flurries, possible 10 to 15cm of precipitation,, freezing level around 1100 metres, winds light from the south west, light to moderate.

Avalanche Summary

Limited reports from Saturday suggest avalanche activity was limited to wind loaded features. More widespread storm slab activity is expected for Saturday night and Sunday as the storm passes through.

Snowpack Summary

Up to 35 cm of recent storm snow is sitting on a variety of layers. A well developed sun crust has formed on solar aspects to surface hoar on shady, sheltered slopes. At lower elevations, a melt-freeze (or rain) crust can be expected in most areas. S Moderate to strong SW winds have formed wind slabs on lee slopes. Below the storm snow, the upper snowpack is generally well settled from the recently warm weather. Two persistent weak layers remain a concern but these problems are becoming more isolated. Before the storm, the early-March crust/facet layer was down roughly 1m and the early-Feb layer is down 1.5m or more. These layers are now deep enough that human-triggering is unlikely, but smaller avalanches or cornices failures have the potential to step down to these layers. Freezing levels have been cycling between valley bottom and 1500-2000m, and low elevation terrain saw significant rain last weekend. The snowpack at lower elevations has been generally stable but wet snow or rain may destabilize the upper layers of the snowpack.

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.