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Avalanche Forecast

Archived

Dec 21st, 2019–Dec 24th, 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.

Sunday afternoon will bring an end to the storm, but continued overnight wind and snowfall will keep the hazard elevated until freezing levels descend and the snowpack has had time to adjust to the load.

Weather Forecast

Weather models are conflicted on snowfall amounts for Saturday night with amounts between 8 to 20cm expected. Strong winds will continue overnight with a lull on Sunday where we may even see some sun. Freezing level is expected to remain around 1700m descending to valley bottom by Monday night.

Snowpack Summary

60cm+ of wet snow and rain in the Cameron Lake area has arrived with extreme northwest winds and a freezing level around 1900m, continuing to load 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

A widespread natural cycle was observed on Saturday along the Red Rock and Akamina parkways, with avalanches to size 2 in the storm snow and some larger ones failing on deep persistent weak layers

Confidence

Forecast snowfall amounts are 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.