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Avalanche Forecast

Archived

Feb 8th, 2016–Feb 9th, 2016

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

Regions

Purcells.

Skyrocketing temperatures are expected to weaken surface snow layers, make cornices extra fragile and possibly wake up deeply buried weak layers.

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

A strong ridge of high pressure is expected to bring sunny skies above valley cloud. Valley cloud tops should be around 1500 m. A warm southerly flow causes alpine temperatures to rise well above 0, with peak warming and sunshine on Tuesday. Some light precipitation may arrive on Thursday with the passage of a warm front.For more details check out https://avalanche.ca/weather.

Avalanche Summary

A natural and artificially-triggered cycle of size 1-3 avalanches occurred on Saturday in response to new snow and very strong winds. The largest events were in the northern Purcells/ Dogtooth Range. These are suspected to have failed on the early January persistent weak layer. Numerous persistent slabs have been triggered in the north over the last couple of weeks. On Friday, a snow cat triggered a size 2 persistent slab on a SE aspect near 2300 m near Golden. Last Saturday, a size 3 sledder-triggered avalanche occurred in the Gorman Creek riding area. Around the same time, a skier triggered a size 3.5 persistent slab a few drainages to the south of Gorman Creek on a north-facing alpine slope. Forecast warming may increase the reactivity of the persistent slab.

Snowpack Summary

Warm temperatures and sunshine are expected to weaken and moisten surface snow layers. Strong to extreme winds on Saturday created wind slabs and cornices in many areas, and scoured north and west-facing alpine slopes. The early January surface hoar/ facet layer is typically down 70-90 cm. Recent very large avalanches have been failing on this interface in the north of the region (see avalanche discussion). In general, the lower snowpack below this layer is well settled and strong, apart from some thin snowpack areas where basal facets exist.

Problems

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.

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.