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Avalanche Forecast

Archived

Mar 14th, 2017–Mar 17th, 2017

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

Regions

Waterton Lakes.

In addition to listed Avalanche Problems, Cornices have also been very active recently. These will continue to grow.  Some will fall.  Bigger than your pickup truck, these are a perfect trigger for Very Large slab avalanches. Know what's above you.

Weather Forecast

Wednesday: Cloudy. Light snowfall (rain below 2100m). Extreme SW wind, easing. Freezing level 2300m. Treeline High 2, Low -1.5Thursday: Snowfall overnight (10-15cm), except rain Below Treeline, easing. Moderate-Strong SW wind. Freezing Level falling to 1500m. Friday: Sunny. Moderate West wind. Freezing level 800m, rising. Treeline Low-8, High -2.5

Snowpack Summary

Warm temperatures have helped Storm slabs bond & settle, but rain to Treeline on Tuesday/Wednesday adds free water to the upper snowpack, while Strong SW winds build slab and cornice higher up. Persistent weak layers in the mid and lower snowpack appear to be waking up, with warmth adding to the stress of near-daily snowfall since February 25.

Avalanche Summary

On Tuesday a Large (Size 3) slab avalanche, up to 2m deep, was observed on a N aspect at 2200m. It ran to valley floor. Several small Loose Wet avalanches were observed in steep terrain Below Treeline. On Sunday, another Size 3 Deep Persistent slab avalanche occurred on a cross-loaded NW aspect, suspected to have failed on deeply buried facets.

Confidence

Forecast snowfall amounts are uncertain on Thursday

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 Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.