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Avalanche Forecast

Archived

Jan 3rd, 2018–Jan 4th, 2018

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

Regions

Purcells.

Tricky conditions warrant a conservative approach. A little warming, precipitation and/or wind-loading could be all we need to awaken a volatile persistent slab, especially at treeline.

Confidence

Moderate - Freezing levels are uncertain

Weather Forecast

Thursday: Clear in the alpine, with valley cloud. A layer of warm air is expected between about 2000-2500 m, while valleys remain cold. Light variable winds. Increasing cloudiness in the evening, with flurries possible overnight.Friday: Cloudy with flurries. Light southwesterly winds.Saturday: Light snow (~5 cm). Light westerly winds.More details can be found in the Mountain Weather Forecast.

Avalanche Summary

Little avalanche activity was reported in the last two days, but whumpfing and cracking was observed in the north of the region on Tuesday between 1700 and 2100 m. Last weekend, a size 1.5 avalanche involving two people near Invermere was reported. It was suspected to have run on the mid-December weak layer. On Saturday a skier triggered a size 2 persistent slab avalanche running on a layer of facetted snow from mid-December. This happened in the north of the region's Dogtooth Range on a west aspect at 2400m. Expect the potential to trigger persistent slabs to increase as last week's storm snow continues to settle into a cohesive slab.

Snowpack Summary

Warming is starting to turn dry powder into a cohesive slab in some areas. The main troublemaker in the snowpack at the moment is a layer of feathery surface hoar down 40-70 cm, buried in mid-December. In places this interface exists as a crust/facet combo. It is most prevalent around treeline, but has been reported as high as 2400 m. A little more warming, precipitation and/or wind-loading could be all that is needed to turn powder into an easy-to-trigger slab above this touchy interface. It's tricky to predict and even professionals are scratching their heads a bit about exactly when and where this beast will wake up. It’s a good time for conservative decision-making.Deeper in the snowpack (about 70-110 cm down), a rain crust from November remains in the back of our minds, but it is considered dormant for now. If you have any recent observations, please share them through the Mountain Information Network.

Problems

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.