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Avalanche Forecast

Archived

Feb 16th, 2015–Feb 17th, 2015

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.

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Confidence

Good - The weather pattern is stable

Weather Forecast

A ridge of high pressure will maintain mostly sunny skies through Wednesday. Freezing levels bounce between valley bottom overnight and 1500-2000 m during the day. It could be even warmer on Wednesday with an above freezing layer near 2500 m. Winds are generally light gusting to moderate from the W-NW. The ridge flattens slightly late on Wednesday and allows a weak system to cross the province on Thursday. This could bring a few centimetres of snow, more cloud, and slightly cooler temperatures.

Avalanche Summary

No new avalanches were observed on Sunday. However, there were a few more reports of previous activity with slabs up to size 3. Sunshine and daytime warming could trigger loose wet sluffs, cornice collapses, and isolated deeper slabs this week.

Snowpack Summary

Expect to find surface crusts on solar aspects and all aspects to at least 2000 m. At alpine elevations, thin new wind slabs or storm slabs may be found and cornices are large and weak. Underneath newly formed near-surface crusts, you may find moist snow. The late-Jan crust/surface hoar layer is 1-2 m deep in the west, and can be found within the upper metre of the snowpack further east. It is variably reactive and still the main concern in many areas. The mid-January surface hoar, deeper again, remains problematic in some areas. The mid-December weak layer may still be on the radar in isolated areas in the east. The mid-November weak layer of crusts and facets can still be found near the bottom of the snowpack. It seems to have been reawakened with warming and has been triggered by explosives during the recent warm spell, taking the entire snowpack with it.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

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.