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Avalanche Forecast

Archived

Apr 26th, 2017–Apr 27th, 2017

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

Regions

Little Yoho.

The big hazards right now are cornices and solar warming. These have a chance of waking up the basal weakness and causing a large avalanche if they happen. Otherwise, watch for sluffing in steeper terrain and enjoy the awesome skiing!

Weather Forecast

Temperatures will remain cool and winds will remain light for the next three days. We should see 5 - 10 cm on Thursday and a few more centimeters on Friday. A ridge is moving in Friday night and Saturday should see drier and sunnier conditions.

Snowpack Summary

Mondays storm brought 10-20 cm below treeline and 30-40 cm in the alpine with light winds. This sits on melt freeze crusts on solar aspects and below 2500m on polar aspects. A surface crust formed to ~1800m on polar aspects on Wed and higher on solar aspects. The basal weakness has been dormant, but will wake up with solar warming or cornice drops.

Avalanche Summary

Some small loose dry sluffing was observed out of steep terrain during brief periods of sun on Wednesday morning. Otherwise, no new avalanches observed or reported.

Confidence

Timing or intensity of solar radiation is uncertain

Problems

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.

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.