Avalanche Forecast

Archived

Apr 24th, 2023–Apr 25th, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Below Threshold.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Below Threshold.

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Below Threshold.

Regions

Jasper, Brazeau, Churchill, Cirrus-Wilson, Fryatt, Icefields, Maligne, Marmot, Miette Lake, Pyramid.

The trend for the next few days is less overnight freeze and increasing freezing levels raising the potential of increased reactivity. Your strategy is to start and end early, avoid cornices, and anticipate natural activity to escalate with full depth releases possible.

Confidence

Low

Avalanche Summary

Monday's Maligne and Icefield's patrols noted nothing new. There was an avalanche Fatality in Banff Park near Lake Louise Saturday from a deep large human triggered slide. Last week a few large cornice triggered avalanches were noted on Alpine East aspects.

Post avalanche observations to the MIN.

Snowpack Summary

A dusting of snow overnight rests on sun crusts on solar aspects and a melt-freeze crust below tree line. Old wind slabs are on exposed alpine terrain. A layer of sun crust or facets linger in the mid-pack. The main concern is the depth hoar and basal facets at the bottom causing our deep persistent slab problem.

Weather Summary

Parkers ridge weather on Monday night will be clear and -4 °C. Tuesday is sun, cloud, flurries, -2 °C, and 1900m freezing level. Wednesday's freezing level is forecast to increase to 2500m and Thursday's will be 3000m.

Terrain and Travel Advice

Cornices become weak with daytime heating.
In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
Avoid exposure to slopes that have cornices overhead.

Problems

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.

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.