Avalanche Forecast

Archived

Mar 31st, 2017–Apr 1st, 2017

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 unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Cariboos.

Forecast wind and light snowfall will see wind slabs and cornices continue to grow. The potential for one of these to release and trigger a deeper persistent slab remains a real concern for Saturday.

Confidence

Moderate -

Weather Forecast

Friday night: Flurries bringing approximately 5 cm of new snow. Moderate to strong south winds.Saturday: Mainly cloudy with continuing flurries bringing approximately 5 cm of new snow. Moderate to strong west winds. Freezing level to 1700 metres with alpine temperatures around -4.Sunday: Mainly cloudy with scattered flurries bringing up to 5 cm of new snow. Light to moderate northwest winds. Freezing level to 1500 metres with alpine temperatures around -7.Monday: A mix of sun and cloud with isolated flurries and a trace of new snow. Light southwest winds. Freezing level to 1600 metres with alpine temperatures around -7.

Avalanche Summary

Reports from Thursday included observations of two large (Size 2.5 and Size 3) storm slabs releasing naturally from steep alpine terrain north of Blue River. Crown fractures of these slides ranged from 60-80 cm. Extensive natural sluffing to Size 2 was also observed, with loose dry activity on northerly aspects and loose wet from solar aspects. One Size 1 cornice fall was also reported.

Snowpack Summary

Up to 40 cm of recent storm snow has fallen at upper elevations. The new snow is dry up high and moist from 1800 m and below. This now brings 40-90 cm of accumulated snow which overlies a rain crust below 2000 m or a sun crust on solar aspects at higher elevations. New wind slabs are developing on leeward slopes and behind terrain features and large, fragile cornices exist along ridgelines. At higher elevations, the February weak layers are down 120-150 cm and woke up during last week's storm with many avalanches stepping down to them. The deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack and a few avalanches and cornice falls have also stepped down to these layers last week resulting in some very large full depth avalanches. These layers remain a real concern while touchier wind slabs, storm slabs and cornices continue to present the risk of acting as triggers for deeper weaknesses.

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.