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Avalanche Forecast

Archived

Apr 19th, 2018–Apr 20th, 2018

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

South Coast Inland.

A buried weak layer in the north of the region remains a concern, as well as pockets of wind slab in high, northerly terrain.  Also be wary of sunny slopes and cornices should the sun make an appearance.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

TONIGHT: Cloudy. Ridge wind light to moderate, southwest. Alpine temperature near -4. Freezing level 1200 m.FRIDAY: Mostly cloudy, flurries beginning overnight. Ridge wind light to moderate, southwest. Alpine temperature near -3. Freezing level 1800 m. SATURDAY: Mix of sun and cloud, light flurries. Accumulation 5-10 cm. Ridge wind moderate to strong, southwest. Alpine temperature near -5. Freezing level 1500 m.SUNDAY: Mostly sunny. Ridge wind light, north. Alpine temperature near -2. Freezing level 1800 m.

Avalanche Summary

Explosive control work in the Duffey Lake area on Wednesday produced a size 3 persistent slab avalanche that propagated over 200 m wide, failing on the late March weak layer. This result was on a west to southwest aspect between 2100-2200 m. Storm slabs up to size 2 were also reactive to explosives near ridge crests and were running far and fast in the recent storm snow.Tuesday there was a report skier's remotely (from a distance) triggering a a size 2 wind slab on a steep east aspect in the Duffey Lake area. Read more details here.On Monday, a large slab avalanche was noted in Duffey Lake Road region in alpine terrain. It was likely triggered by a cornice fall during sunny and warm conditions. The slab likely failed on the late March weak layer. Large (size 3) persistent slab avalanches were observed in the far north of the region over the weekend. They were about 60 to 80 cm deep, on northwest to east aspects, between 1800 and 2200 m, and failed naturally on the weak late March surface hoar layer. These propagated widely across the slopes. Many slides in the recent storm snow were also observed, often triggered by cornice failures.

Snowpack Summary

20 to 40 cm of recent snow (highest amounts near Coquihalla Highway) has been redistributed into lee terrain features from northeast switching to southwest winds. This overlies variable surfaces, including wind slabs at high elevations, and crusts on all aspects up to at least 2000 m, and possibly higher on south aspects.A weak layer consisting of surface hoar, facets, and/or a melt-freeze crust from late March is now buried about 50 to 100 cm. This layer is spotty in its distribution and has recently produced large and destructive avalanches. It is mostly likely to be problematic on west, north, and east aspects between 1900 m and 2250 m.The mid and lower snowpack are well-settled and strong.

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.

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.

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.