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Avalanche Forecast

Archived

Feb 10th, 2017–Feb 13th, 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 unlikely, human triggered possible.
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, human triggered possible.

Regions

Waterton Lakes.

We are just reaching the tail end of a widespread cycle of large natural avalanches. Begin your weekend with very conservative terrain choices, avoid high-consequence terrain, and watch for indications of instability.

Weather Forecast

A cooling/drying trend through Saturday, then warming into next week.Saturday: Light snowfall (with Extreme winds) eases early Saturday to Flurries and Strong Westerly winds. High -8Sunday: Mainly clear, Strong Westerlies. Treeline High of -7. Alpine Temperature inversion. Monday: Clear, Moderate Westerlies. Temperature inversion, highs near 0.

Snowpack Summary

On Thursday, rain fell below 1850m, with 10-40cm snowfall above redistributed by Strong SW - W winds, adding more load atop 120cm of recent storm snow from last weekend. This all sits on crust, or facets, Below Treeline; and hard smooth surfaces in all open areas. Facets deep in the snowpack (& a deeper crust) may be reactive under the new load.

Avalanche Summary

On Thursday and Friday, fresh Natural avalanche activity was visible in most paths observed. Many of these were large (Size 2 - 3). This included numerous avalanches from windward and front range locations that are typically wind-scoured scree, but are now holding snow. Natural triggering is expected to taper off over the weekend.

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.

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.