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Avalanche Forecast

Archived

Nov 16th, 2021–Nov 17th, 2021

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

Regions

Little Yoho.

Although the storm has passed and the temperatures have cooled, large avalanches were directly observed today. The storm snow needs more time to settle and bond.

Weather Forecast

Cooler temperatures are expected over the next few days with valley temps staying below zero. Minimal precip associated with a benign weather pattern is expected. The wind could be the most intense input with wind speed well in to strong range from the West on Thursday.

Snowpack Summary

Up to 80cm of storm snow since Friday with moderate SW winds have created windslabs in the alpine and at treeline and storm slabs at all elevations. This buries a relatively thin, facetted snowpack with a couple crusts in it. Total snow depths are 60-100cm at treeline with more in the alpine. Below 2000m, rain has saturated the snowpack.

Avalanche Summary

Forecasters observed the remnants of the cycle that ended with the cooling of temperatures this morning. Storms slabs up to size 3.5 were observed throughout Banff, Yoho and Kootenay highway corridors. Today, Lake Louise reported triggering a size 3 avalanche 250m wide on the Nov 5th crust using explosives.

Confidence

Due to the number and quality of field observations

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.

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.