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Avalanche Forecast

Archived

Mar 16th, 2017–Mar 19th, 2017

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

Regions

Waterton Lakes.

Avoid traveling below slopes overhung by cornices. Pay attention to precipitation amounts and freezing levels on Saturday - danger will vary accordingly. Avoid traveling through avalanche runout zones during periods of heavy loading.

Weather Forecast

Friday: Clear, becoming cloudy. Light-Moderate SW wind. Freezing level 500m, rising to 1800m. Treeline Low-8, High -2.5Saturday: Rain/Snow, heavy in the West. Freezing Level 2450m. Extreme SW winds.Sunday: Clearing. Strong SW winds, easing. Freezing level 1000m. Treeline Low -10, High -9

Snowpack Summary

Rain (upto 45mm) on Tuesday and Thursday turned the snowpack moist at Treeline and Below. A surface freeze temporarily increases stability for Friday.  Strong SW winds are building slab and cornices higher up. All the recent snow and warmth has deep Persistent weak layers hovering around tipping point in isolated features.

Avalanche Summary

On Thursday a size 2.5 Deep Persistent slab was observed from a cross-loaded, typically rocky slope in the Alpine. This failed near ground on a NW aspect at 2200m. Two other Deep Persistent slabs (Size 3) were observed during the past week, running from the Alpine to Valley bottom. Numerous Large, Loose Wet avalanches were observed on Wednesday.

Confidence

Intensity of incoming weather systems is uncertain on Saturday

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.