Avalanche Forecast

Archived

Apr 8th, 2012–Apr 9th, 2012

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

South Coast.

Confidence

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

Weather Forecast

Monday: Clouds with scattered light precipitation. Freezing level rising to around 1800m. Light southerly winds. Tuesday: Light precipitation. Freezing level rising to around 2400m in the afternoon. Wednesday: Light to moderate precipitation. Freezing level falling to 1500m this evening.

Avalanche Summary

A size 2 skier-triggered avalanche was reported in the Duffey Lake area on Friday. It was triggered on a NE facing alpine slope and is suspected to have failed on the late March sun crust. There have also been reports of isolated natural slab avalanches to size 2.5, primarily on solar aspects during the afternoon. Loose wet activity continues on steep solar aspects.

Snowpack Summary

The snow surface consists of old wind slabs in exposed alpine terrain, spotty surface hoar on shady slopes, and a sun crust/moist snow on solar aspects. This sits on up to a metre of settling storm snow from last week. The March 27 layer is predominately a crusty interface except on north facing slopes at treeline and above where small surface hoar (5mm) may be found. It's now down 60-120 cm and has recently exhibited hard, sudden results and a Rutschblock 4 whole block failure in the Duffey Lake area. Deep persistent weaknesses linger in many colder and shallower snowpack areas. Daytime warming and sun-exposure may cause surface snow to lose cohesion and cornices to weaken.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.