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Avalanche Forecast

Archived

Mar 10th, 2017–Mar 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 and human triggered avalanches likely.
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.

Recent storm snow has not yet settled.  New snow, wind loading and warming temperatures will add to instability.  Cornices are large, and could trigger deep layers. This is a time to stick to conservative terrain without overhead hazard.

Weather Forecast

Current forecasts vary widely- use discretion.Saturday: Sun+cloud, becoming light snowfall in the afternoon. Treeline high -2.5. Temperature inversion. Moderate - Strong SW winds. 10-20cm of snowfall expected Saturday overnight. Sunday: Cloudy. Treeline High -4. Moderate W winds. Mon: Sun & Flurries. Treeline high -1, Moderate-Strong W winds

Snowpack Summary

25 - 40cm of new snow has fallen over Thursday/Friday. Moderate SW winds with near-freezing temperatures above 1800m continue to redistribute these into Storm Slabs, especially on lee slopes. An interface now down 45cm gave Easy, sudden shears on Thursday. Daily snowfall since Feb 25 may be stressing a thick, dense facet layer deep in the snowpack.

Avalanche Summary

On Thursday, a Large Storm Slab avalanche was observed at Treeline(2050m), on a steep, open N aspect below large cliffs. Numerous Small Loose Dry avalanches were observed in steep terrain. A few other slab avalanches (Size 1 -2)were observed in the Alpine, but observations were hampered by visibility. Poor visibility limited observations on Friday.

Confidence

Due to the number of field observations on Friday

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

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.