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Avalanche Forecast

Archived

Apr 21st, 2014–Apr 22nd, 2014

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

Little Yoho.

High freezing levels and rain will raise the avalanche danger and make for poor travel conditions at lower elevations. We have low confidence in the accuracy of the weather forecast, so pay attention to temps/ precip at the local level.

Weather Forecast

Tues: High freezing levels (2400m in the north and west - 2700m in the south and east) and 5-10 mm of precipitation. Moderate south winds at ridgetop. Precip amounts may vary locally Wed and Thurs: Cooling with freezing levels dropping to 1000 - 1600m, light precipitation and winds switching to moderate from the west.

Snowpack Summary

10-30 cm's of recent new snow with moderate W winds has formed some soft slabs at ridgetop on N-E aspects. Warm temps are causing these to settle out quickly. Temperature crusts exist to 2200m on polar aspects and higher on solar aspects. The midpack is generally strong, however the basal facets persist especially in thin snowpack areas.

Avalanche Summary

Some pinwheeling and wet loose avalanches to size 1 out of steep solar, otherwise, no new avalanches were observed or reported today. 

Confidence

Timing, track, or intensity of incoming weather system is uncertain on Tuesday

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.

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.

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.