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Avalanche Forecast

Archived

Apr 22nd, 2012–Apr 23rd, 2012

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

Regions

Kootenay Boundary.

Confidence

Good

Weather Forecast

Clear skies are forecast for Monday. Ridgetop winds are expected to be light from the southwest with freezing levels reaching 3300m.

Avalanche Summary

No new avalanches have been reported from the region. This may speak more to the lack of professional observations at this time rather than actual conditions. I would expect wet natural avalanche activity on Monday resulting from forecast rising freezing levels and strong solar input.

Snowpack Summary

Recently formed windslabs have most likely settled and gained considerable strength with the warm temperatures over the weekend, and in most places transitioned into wet slabs. Below this, spring weather has left us with wet grains or melt-freeze crusts at treeline and above while warm temperatures have continued to penetrate and weaken the isothermal snowpack at lower elevations. The mid-February buried surface hoar layer is down about 140-220 cm. The likelihood of avalanches failing on this layer has been very low due to cooler temperatures, however it may wake up with warming and the consequence continues to be very large destructive avalanches. Cornices in the region are very large and have may become weak with spring temperatures.

Problems

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.

Wet Slabs

Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.

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.