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Avalanche Forecast

Archived

Nov 28th, 2021–Nov 29th, 2021

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

Regions

Little Yoho.

Forecasters are uncertain about snowfall amounts Sunday night into Monday. Don't be surprised if there is more than anticipated. If this is the case, the avalanche danger will be HIGH in the Alpine on Monday.

Weather Forecast

The temperature is supposed to cool slightly and the precipitation to taper off by Monday morning. Although the wind did not materialize today, it is expected to be in the strong range from the West on Monday. Another warm wave of precip is expected Tuesday afternoon.

Snowpack Summary

35-45cm of snow since Thurs. In some locations this new snow is not bonding well to underlying hard surfaces. The Nov 15 crust is 35-60 cm down and present up to 2100 m. The Nov 5 crust/facet layer exists near the ground. Snowpack depths at tree-line average 80-110 cm.

Avalanche Summary

Lake Louise reported triggering 2 size 2 avalanches with explosives. Both slides ran on the Nov 5 crust. A size 2 was observed over Pilsner Pillar, but it was hard to determine how recent the slide was. More avalanche activity is expected on Monday, but it will depend on snowfall amounts overnight on Sunday.

Confidence

Due to the number and quality of field observations on Sunday

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

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.