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Avalanche Forecast

Archived

Mar 9th, 2013–Mar 10th, 2013

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

Regions

South Columbia.

Confidence

Poor - Timing, track, or intensity of incoming weather is uncertain for the entire period

Weather Forecast

Sunday: Increasing cloud with a chance of flurries late in the day. The freezing level climbs to 1500 m during the day. Winds are moderate from the west-southwest. Monday: Sunny breaks and a chance of flurries. Temperatures are a degree or two cooler with the freezing level around 1000 m. Winds ease to light from the northwest. Tuesday: Moderate snow. The freezing level could rise to around 1600 m and winds increase to moderate or strong from the southwest.

Avalanche Summary

Loose snow sluffing continues in steep terrain on all aspects. On Thursday there was a report from the Central Selkirks of a chunk of snow that fell out of some cliffy terrain at treeline which triggered and propagated three progressively deeper slabs resulting in a size 2.5 avalanche sliding on the February 12th weak layer down about 100 cm.

Snowpack Summary

A fairly widespread layer of surface hoar, mixed with a dusting of new snow in some areas, is sitting above various sun crusts and old storm slabs. The storm slab continues to settle, and is becoming more stubborn to trigger. The weak layer of surface hoar that was buried on February 12th is now down about 100-150 cm and continues to be triggered by light additional loads on Southerly aspects where it is sitting on an old sun crust. Larger loads like cornice fall or explosives have been able to trigger this layer on various aspects in the alpine and at treeline. If the we get a period of strong solar radiation, then we may see another cycle of natural activity on Southerly aspects resulting in large destructive avalanches.

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.

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.