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Avalanche Forecast

Archived

Mar 30th, 2013–Mar 31st, 2013

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

Regions

Purcells.

Danger could INCREASE TO CONSIDERABLE with intense radiation on south and west aspects, especially at treeline and below. Be aware of how the warm weather is changing the snowpack. 

Confidence

Good

Weather Forecast

A dominating high pressure system with sunny skies, rising freezing levels and light winds continues through to Monday. The pattern will start to deteriorate by Tuesday, showing increased cloud and grey skies with no precipitation. Sunday: Few to scattered high cloud. Alpine temperatures 4.0 and freezing levels 2600 m. Ridgetop winds light from the NW.Monday: Scattered clouds. Alpine temperatures 5.0 and freezing levels rising to 2600 m. Ridgetop winds blowing light from the NW.Tuesday: Cloudy. Alpine temperatures -1.0 and freezing levels falling to 2300 m. Ridgetop winds blowing light from the SW.

Avalanche Summary

Numerous natural loose wet avalanches up to size 1.5 and one natural cornice fall size 2.5, not pulling a slab on the slope below.

Snowpack Summary

Surface faceting and surface hoar growth (up to 20 mm) has been prevalent on most aspects and elevations, while the surface snow on sun-exposed slopes and at lower elevations has been subject to daily melt-freeze cycles.Cornices are large and weak. Pockets of wind slab can be found on lee slopes and possible to trigger under your skies or sled. A layer of buried surface hoar sitting on a crust down around 70-120cm, and has been producing variable results in snowpack tests. This persistent weakness remains a concern because of the potential for very large avalanches particularly with heavy triggers such as cornice falls. Old deep persistent weaknesses, including basal depth hoar, are a concern in shallow snowpack areas.

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.

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.

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.