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Avalanche Forecast

Archived

Apr 16th, 2019–Apr 17th, 2019

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

Regions

Lizard-Flathead.

Overnight winds are expected to keep slab problems firmly on the radar for Wednesday. The crust under our new snow hasn't been a great bonding surface and wind loading won't help matters.

Confidence

Moderate -

Weather Forecast

Tuesday night: Increasing cloud with a chance of isolated flurries. Winds increasing to moderate or strong from the southwest. Freezing level remaining near 1700 metres.

Wednesday: Mainly cloudy with isolated wet flurries with a possible trace of new snow above 1800 metres. Light rain below. Moderate to strong southwest winds. Alpine high temperatures around +1 with freezing levels peaking at 2200 metres and rising overnight.

Thursday: Mainly cloudy. Moderate to strong southwest winds. Alpine high temperatures around +6 with freezing levels rising to 2800 metres, remaining elevated overnight.

Friday: Cloudy with showers bringing 5-10 mm of rain to mountaintop. Strong southwest winds. Alpine high temperatures around +6 with freezing levels dropping from 2800 to 2500 metres over the day

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, and this was well before the storm really kicked into gear.

Snowpack Summary

The Fernie Factor really kicked in late Saturday into early Sunday. The region picked up about 30 cm of snow (and 53 mm of water). Check out this great MIN report from Sunday. This snow sits above a widespread supportive crust. Steep, north facing, alpine terrain may still hold a cold, dry, snowpack where fresh storm slabs are thought to be widespread. Steep north facing terrain is also harboring a deeply buried layer of facets. Although unlikely, human triggering of persistent slabs on this layer may still be possible, especially in rocky alpine terrain with a shallow or highly variable depth snowpack.

It looks like it is going to warm up this week and all the new snow will likely produce a widespread and powerful loose wet cycle. During the heat of the day, especially under direct sun, the snow surface will become moist or wet almost everywhere (except for high elevation north) and loose wet avalanches could run far.

Below treeline the snowpack has melted or is isothermal.

Problems

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.

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.