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Avalanche Forecast

Archived

Mar 17th, 2014–Mar 20th, 2014

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

Regions

Waterton Lakes.

New snow on top of crusts and rain soaked snow are adding to an already complex snowpack. The hazard will be higher on South facing slopes if there is significant solar radiation Tue. Hazard will also increase Wed depending on snowfall amounts.

Weather Forecast

After receiving 30-40cm over the last 48hr the snowfall will taper off tonight. Tue will be a bit of a lull but then the next system arrives on Wed with possibly another 25cm by Fri. Temperatures will be cooler, with daytime highs in the -5 to 10 ranger. Winds will return to the Waterton 'normal' of strong westerlies for the forecast period.

Snowpack Summary

Sundays rain left moist snow and crust that are now 30-40 under the surface. Below 1900 there is a complex of crusts and moist snow 40-45cm thick. Above 1900m the crusts are more discrete, with dry snow in between. The Feb facet layer is still persistent, down 70-180cm and could still be reactive in places that have not already gone.

Avalanche Summary

Not much avalanche activity has been seen Sun/Mon because of poor visibility. A long audible avalanche was heard off the back of Cameron Lake on Mon. This was likely the storm snow running on the Mar 14 melt freeze crust.

Confidence

Intensity of incoming weather systems is uncertain on Wednesday

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.

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.

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.