Avalanche Forecast

Archived

May 4th, 2023–May 5th, 2023

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural and human triggered avalanches likely.

Alpine

Below Threshold.

Treeline

Below Threshold.

Below Treeline

Below Threshold.

Alpine

Below Threshold.

Treeline

Below Threshold.

Below Treeline

Below Threshold.

Regions

Banff Yoho Kootenay, Little Yoho, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

The hot weather will persist for one more day before freezing levels show an appreciable drop as weather approaches. Dangerous avalanche conditions will persist at least until this change occurs.

Hikers and scramblers: expect poor travel and avoid all avalanche terrain.

Confidence

Moderate

Avalanche Summary

A widespread natural avalanche cycle to size 4 continues with avalanches failing on the ground on all aspects and elevations, many running to the valley bottom. This is the biggest avalanche cycle of the season. Click the link's for recent avalanche info on the Plain of Six Glaciers and Lake Louise area.

Snowpack Summary

The heat has penetrated the snowpack and destabilized it at all elevations. Warm temperatures overnight have prevented all but superficial refreezing.

Expect snow on all aspects at all elevation to be unsupportive isothermal (slush).

Weather Summary

The ridge of high pressure that has dominated for a week has started to break down with unstable air allowing for afternoon thundershowers and spotty rain over the last two evenings. High freezing levels will remain Thursday evening with overnight clearing bringing sunny skies in the AM for one more kick at 3500m freeze levels Friday.

Clouds will work their way in Friday afternoon and lead to light rain as freezing levels drop to 2500m overnight that will turn to snow at alpine elevations.

Terrain and Travel Advice

Avoid all avalanche terrain during periods of intense solar radiation.
Avoid exposure to overhead avalanche terrain as temperatures increase.

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.