Avalanche Forecast

Archived

Mar 8th, 2013–Mar 9th, 2013

Alpine

Natural avalanches possible, human triggered probable.

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, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Purcells.

Confidence

Poor - Timing, track, or intensity of incoming weather is uncertain on Sunday

Weather Forecast

Friday night and Saturday: The dominating feature is a ridge of high pressure over the whole province bringing warmer air (-4 in the alpine), freezing levels rising to 1600 m., clear skies and light NW winds. Sunday: The ridge is breaking down in the North and remains in the Southern part of the interior range. There is a chance of light precipitation for Sunday (5-10 mm) with winds picking up in the moderate range from the W. Temperatures are slightly cooler than Saturday.Monday: Another system which could deliver more precipitation is expected for Monday but the timing and intensity is still uncertain.

Avalanche Summary

Several natural and skier triggered loose dry avalanches size 1 were reported which ran in the new snow in steep rocky terrain.

Snowpack Summary

The solar radiation and temperatures increasing tomorrow (especially in the Southern part of the region) will weaken the surface of the snowpack especially on S facing slopes. This could possibly trigger the recent wind slabs in the alpine lee areas and below lee ridgetop at treeline. Large looming cornices exist on ridgelines and could also be triggered by the warmth and sun creating a significant load on the slopes below. Buried beneath (60-90 cm) exists a surface hoar and a sun crust layer, which continue to be lingering concerns. A cornice fall could trigger this deeper instability potentially creating large avalanches.

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.