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Avalanche Forecast

Archived

Apr 5th, 2014–Apr 6th, 2014

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

Regions

South Coast.

What's going to happen to the snowpack if it warms up significantly on Sunday/Monday/Tuesday? Read a discussion here...

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Sunday

Weather Forecast

A mix of sun and cloud for Sunday. Unsettled conditions, bringing light-moderate precipitation amounts, cloudy skies and rising freezing levels through Tuesday. Sunday: Mix of sun and cloud. Freezing levels rising to 1600 m. Alpine temperatures near zero degrees. Ridgetop winds moderate from the SW.Monday/ Tuesday: Freezing levels rising to 1700 m with no re-freeze overnight. Up to 20 mm expected by Tuesday. Alpine temperatures near 2.0 degrees. Ridgetop winds remain strong from the SW.

Avalanche Summary

On Wednesday, a cornice fall on a steep north facing features at 2300m initiated a size 3 avalanche. It likely ran on the early March melt-freeze crust.Small loose dry avalanches were seen from steep rocky terrain features. Loose wet avalanches were also seen on solar aspects. I suspect natural activity will continue with the solar influence on Sunday and the warmer temperatures through Monday/Tuesday. Smaller surface avalanches may trigger deeper weak layers, especially in thinner snowpack areas.

Snowpack Summary

Up to 15 cm of new snow sits above a mix of surface hoar, facets and melt freeze crusts. The new snow seems to have a poor bond to old surfaces and isolated wind slabs likely exist. Solar radiation will likely weaken the snow surfaces and become moist or wet. Recent warm temperatures have helped to settle and strengthen the upper snowpack and snowpack tests have been producing hard resistant planar shears on the late March crust down 30-50 cm. The persistent weak layers from early March and early February continue to be a concern. The March melt-freeze crust/surface hoar is reported to be down 60 - 100cm. The February crust/facet/surface hoar layer is now deeply buried down 150 - 250cm. These layers are mostly inactive at this time, but could re-awaken with extended warming, solar influence and precipitation through the forecast period.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.