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Avalanche Forecast

Archived

Feb 18th, 2019–Feb 21st, 2019

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

Regions

Waterton Lakes.

Wind slabs will continue to form on all aspects as winds change throughout the forecast period. Ski quality below treeline is excellent.

Weather Forecast

Tuesday: Cloudy with isolated flurries, increasing moderate winds from the SW. Alpine High -13.Wednesday: Cloudy with isolated flurries, with winds switching to NE gusting to 40km/h. Alpine High -9Thursday: Mix of sun and cloud. Light NE winds and an alpine high of -15

Snowpack Summary

25-40cm of recent snow formed windslabs from moderate SW winds over the past week that are now buried and difficult to identify. More recent N winds have also formed slabs immediately below ridge crests. The midpack is strong in deep snowpack areas but this increase in loading will stress the weak, facetted basal snowpack.

Avalanche Summary

Evidence of natural windslabs from the storm was seen on a field trip to Cameron Lake area on Monday, with a few more natural recent loose dry avalanches out of steep rocky terrain. Surrounding operations have been seeing natural and skier triggered windslabs to size 1.5.

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.

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.