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Avalanche Forecast

Archived

Dec 20th, 2019–Dec 23rd, 2019

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

Waterton Lakes.

The storm rages on! Wet snow and rain will continue to load the snowpack on Friday night into Saturday. This continues to be a good time to avoid avalanche terrain.

Weather Forecast

Heavy wet snow or rain will continue Friday night and possibly Saturday with 110km/h winds and freezing levels near 2000m. There is some disagreement in the weather models on how much precipitation will arrive on Friday night and Saturday with amounts between 10 and 30cm, but the main event should be over by Sunday.

Snowpack Summary

30cm of wet snow and rain has arrived with extreme northwest winds and a freezing level around 1900m, providing a shock to the snowpack. A weak crust facet combo formed in November is down 60cm, and additional crust/facet layers formed in October form the bottom of the snowpack.

Avalanche Summary

No recent natural activity has been observed but visibility is poor. You can be sure slabs are building where the precipitation has come as snow.

Confidence

Intensity of incoming weather systems 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.