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Avalanche Forecast

Archived

Dec 18th, 2018–Dec 19th, 2018

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

Regions

South Coast Inland.

A brief break between storms on Wednesday. Expect avalanche danger to rise on Thursday as another Pacific frontal system impacts the region.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

TUESDAY NIGHT: Flurries, accumulation 5-10cm. Alpine temperature -4. Moderate to strong southwest wind. Freezing level 1100m. WEDNESDAY: Scattered flurries, accumulation 5 cm. Alpine temperature -2. Light west wind. Freezing level 1300m. THURSDAY: Heavy snowfall, accumulation 20-30 cm. Alpine temperature -1. Moderate to strong southwest wind. Freezing level 1500m. FRIDAY: Cloudy with sunny breaks. Alpine temperature -5. Light west wind. Freezing level 300m.

Avalanche Summary

There was a report of natural avalanche in the Duffy Lake area on Monday. This appears to be a size 2 that was 60 cm thick and 80 m wide on a southeast slope at tree line. Click here to see the MIN post.

Snowpack Summary

Another storm has brought an additional 20-30cm of snow to the region at upper elevations. Strong southerly winds have distributed new snow into variable wind slabs in exposed locations.Below the recent storm snow lies a weak layer, comprising 20-30 cm of low density faceted snow. Initially, the snow did not bond well to this layer. While it's likely gaining strength, field observations show that slab avalanches remain possible on this layer.Near the base of the snowpack, a crust exists that previously had sugary facets. This could potentially still be of concern in high north facing areas in drier parts of the region. Elsewhere, this layer is no longer a concern.

Problems

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.

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.