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Avalanche Forecast

Archived

Mar 20th, 2018–Mar 21st, 2018

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

Regions

Northwest Coastal.

The best skiing and riding conditions are likely found on northerly aspects at upper elevations. Pay attention to changing conditions if the sun comes out.

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain on Thursday

Weather Forecast

Wednesday: Mix of sun and cloud with light precipitation. Alpine temperatures near -1.0 and freezing levels at valley bottom. Ridgetop winds light gusting strong from the northeast. Thursday: 10-20 cm of new snow in upper elevations accompanied by strong ridgetop winds from the East. Freezing levels near 500 m and rising through the day to 1200 m. Friday: Cloudy with isolated flurries. Alpine high of -3 and freezing levels near 700 m. Light winds from the East.

Avalanche Summary

On Monday, we received reports of a skier triggered size 1 wind slab on a north-east aspect near 1600m elevation. The slab averaged 20cm thickness and ran on the March 9th surface hoar / facet layer.Last weekend, the region was active with a range of reports from large size 3 wet slabs which stepped down to the mid-December ice layer to a remotely triggered persistent slab (size 2), which stepped down to the mid-January surface hoar interface, running on an east aspect near 1600m.

Snowpack Summary

The snowpack consists of a wide variety of snow surfaces, including up to 20 cm of new snow at higher elevations, pockets of wind slab, a melt-freeze crust on south-west aspects an wet snow down low, On March 9th, surface hoar and/or smaller facets (on sheltered, shady aspects) were buried by the last significant snowfall down 10-25 cm. This layer was reactive to skier triggers in some areas on Monday. Deeper in the mid-pack, layers of crusts, facets, and isolated surface hoar buried 50 to 100 cm exist from mid- and late-February and a surface hoar/ crust layer from January is buried around 150 to 200 cm. Near the bottom of the snowpack, sugary facets exist in colder and dryer parts of the region, such as the far north.

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.