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Avalanche Forecast

Archived

Dec 18th, 2020–Dec 19th, 2020

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

Regions

Glacier.

The AVALANCHE danger is increasing with the building storm slab over  weak surface hoar. Make conservative terrain choices.

Weather Forecast

Flurries today with another 7cm of accumulation.

Alpine high of -6C with ridge winds SW moderate to strong.

Freezing level 1200m.

Tonight through Sunday upwards of 30cm storm snow accompanied by SW winds moderate gusting to extreme.

Snowpack Summary

Wind, warmth and continued snowfall have formed a sensitive storm slab at all elevations over the Dec 13 surface hoar layer. Weak layers of concern are Dec 13 surface hoar down 45cm+ and Dec 7 crust/surface hoar layer down 65cm+. The Nov 5 crust has been unreactive to stability tests.

Avalanche Summary

Numerous size 1-2 skier remote avalanches were triggered yesterday both in the west end of the park and the Asukan and Illecillewaet valleys. On Wednesday a skier went for a ride in a size 1.5 slide below treeline elevation. Numerous avalanches to size 3.5 were recorded in the highway corridor yesterday.

Confidence

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

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.