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Avalanche Forecast

Archived

Apr 4th, 2016–Apr 5th, 2016

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

Regions

South Rockies.

Choose a conservative route. The spring snowpack has been very active, with large avalanches failing naturally.

Confidence

Moderate - Timing or intensity of solar radiation is uncertain on Tuesday

Weather Forecast

Cloud, moderate to strong NW winds and a few snow showers may linger on Tuesday morning, before a ridge brings dry and very warm weather again for the remainder of the week. Freezing levels of around 1700 m on Tuesday are expected to climb above 3000 m by Wednesday.

Avalanche Summary

A cycle of large natural avalanches has been reported from the north Elk Valley, which occurred on Friday and Saturday. At least one of these appears to be a persistent slab, and all were likely to have been triggered by warming. A size 2.5 storm slab also released in steep rocky terrain in the south-east on Friday. With skyrocketing temperatures predicted this week, I would expect further large/deep natural avalanche activity.

Snowpack Summary

Large cornices overhang alpine slopes. Glide cracks have opened up on several slopes and herald more glide avalanches to come. Variable surface crusts exist. Low elevation and thin snowpack areas have become isothermal. Deeply buried weak layers in the mid snowpack and near the ground appear to have woken up in some areas with prolonged warming (see avalanche discussion).

Problems

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.

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.