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Avalanche Forecast

Archived

Apr 27th, 2017–Apr 28th, 2017

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

Jasper.

Pay close attention to freezing levels as we move into spring-like conditions. The avalanche danger will increase with rain, solar exposure and daytime heating.

Weather Forecast

With the Jet Stream to the South cool temps dominate to the weekend. Snowfall or rain will tapper off by Friday AM. With freezing levels descending to the valley bottomĀ  snowpack overnight recovery will be good. Winds remaining light N to W. Daytime freezing levels will be close to 2,000m,

Snowpack Summary

On Northerly facing slopes above treeline up to 20 cm of loose new snow sits over a well consolidated upper snowpack. Melt freeze crusts are ubiquitous to treeline above which their distribution narrows to solar slopes up to 2600m. The mid-pack is consolidated and bridges the weak base. The bottom snowpack is a mix of weak facets and depth hoar.

Avalanche Summary

Avalanche activity will increase with thermal inputs such as rain, direct solar radiation and daytime warming. During the morning and after a good nights freeze the danger will gradually increase during the day. Typically it will be at it's greatest from 14:00. Likely trigger spots are from shallow rocks, cliffy terrain and shallow snowpack areas.

Confidence

Freezing levels are uncertain on Sunday

Problems

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

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.