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Avalanche Forecast

Archived

Dec 19th, 2018–Dec 20th, 2018

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

Regions

South Coast Inland.

HIGH danger is forecast for Thursday. Expect rapid snow loading and very strong winds. It is a good day to avoid avalanche terrain and stick to sufficiently low-angled slopes and densely-spaced trees.

Confidence

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

Weather Forecast

WEDNESDAY NIGHT: Cloudy with light snowfall, accumulation 5 to 10cm. THURSDAY: Cloudy with snowfall, accumulation 20 to 30cm with local amounts up to 50cm, strong to extreme southwest winds, alpine temperature -1°c, freezing level rising to 1600m over the day. FRIDAY: Partly cloudy, moderate west winds, alpine temperature -9°c, freezing level 600m. SATURDAY: Cloudy with light snowfall, accumulation 5cm, moderate southwest winds, alpine temperature -7°c, freezing level 500m.

Avalanche Summary

There was a report of natural avalanche in the Duffey Lake Road 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. Expect to see similar avalanches during Thursdays storm.

Snowpack Summary

Up to 40 cm of snow fell on Wednesday around the Coquihalla, with substantially lesser amounts in the north of the region. We are in the midst of another storm impacting the region on Thursday, which will bring more snow and strong to extreme southwest winds. Expect the new snow to be reactive to both skier activity and natural triggers.A weak layer of facets and surface hoar lies below all this storm snow. While the layer is likely gaining strength, field observations show that slab avalanches remain possible on this layer where it exists.Near the base of the snowpack, a crust exists with weak and sugary facets beneath it. This could potentially still be of concern in high north-facing aspects where the snowpack rests on very smooth ground cover. Elsewhere, this layer is no longer a concern.

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.

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.