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Avalanche Forecast

Archived

Feb 18th, 2019–Feb 19th, 2019

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

South Coast.

Forecast updated 12:00 Tuesday.An unusual weak layer makes steep and convex terrain features particularly dangerous.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

MONDAY NIGHT: Cloudy, moderate northwest wind, alpine temperatures drop to -6 C.TUESDAY: Cloudy with light flurries, accumulations of 3-8 cm, moderate northwest wind, alpine high temperatures around -3 C.WEDNESDAY: Mix of sun and cloud, light north wind, freezing level climbing to 900 m, alpine high temperatures around 0 C.THURSDAY: Mostly sunny, light northeast wind, alpine high temperatures around -2 C.

Avalanche Summary

Storm slab avalanches may still be possible to trigger as they slowly bond to underlying crusts.On Monday, search and rescue responded to an avalanche in the Mount Seymour backcountry. The avalanche occurred on a steep feature at treeline elevation (see photo here). At the time of publishing there limited details about this avalanche.Over the weekend, a few whumpfs and small (size 1) skier triggered avalanches were reported. On Friday, widespread avalanche activity was reported in the North Shore mountains. Ski cutting produced numerous small (size 1) slab avalanches in the top 30 cm of snow, as well a few notable larger avalanches (up to size 2.5). These avalanches showed impressive propagation, with some being triggered remotely (from a distance) and on a few occasions stepping down to a 50 cm deep crust layer.

Snowpack Summary

30-50 cm of recent storm snow is slowly bonding to underlying crust layers. Because of the recent cold temperatures and weak snow around the crusts, storm slabs are expected to take longer than usual to strengthen. New sun crusts may be found near the surface of south-facing aspects, while wind slabs may be found in exposed terrain. The lower snowpack is 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.