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Avalanche Forecast

Archived

Apr 17th, 2019–Apr 18th, 2019

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, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Lizard-Flathead.

First warm, then rain. A one-two punch over the coming few days is expected to maintain active loose wet avalanche conditions while bringing a test to any slabs that haven't quite bonded to the crust.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Wednesday night: Mainly clear. Moderate to strong southwest winds. Freezing level remaining near 2300 metres.

Thursday: Mainly sunny with cloud increasing over the day and showers beginning in the evening. Moderate to strong southwest winds increasing over the day. Alpine high temperatures around +4 with freezing levels rising to 3000 metres and remaining elevated overnight.

Friday: Cloudy with light rain showers, increasing and transitioning to flurries in the alpine overnight. Moderate to strong southwest winds. Alpine high temperatures around +5 with freezing levels dropping from 3000 to 2500 metres over the day.

Saturday: Cloudy with continuing rain showers and the possibility of 10-15 cm of wet new snow accumulating in the alpine, including overnight accumulations. Light variable winds. Alpine high temperatures around 0 with freezing levels to 2000 metres.

Avalanche Summary

On Sunday skier triggered avalanches were widespread on north through east facing slopes in the alpine and down into treeline too.

A natural avalanche cycle occurred Saturday night, the highlights were storm slabs up to size 2 on northeast facing alpine terrain around 1700 m. A natural cornice failure was observed from a north facing ridgeline which subsequently triggered a size 2.5 storm slab involving the new snow. Control work produced storm slabs to size 2. We received a great MIN report of a small storm slab from Saturday morning in the first hours of the storm.

Snowpack Summary

New sun and temperature crusts are likely to be found on the surface on solar aspects and below the alpine, having formed above the 30 cm of dense snow from the past weekend's storm. In most areas, this storm snow sits above a widespread supportive crust.

North facing alpine terrain may still hold a cold, dry snowpack. High elevation north facing terrain also harbours a deeply buried layer of facets. Although unlikely, human triggering of persistent slabs on this layer may still be possible in rocky alpine terrain with shallow or variable snowpack depth.

Below treeline the snowpack has melted or is isothermal.

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.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.