Avalanche Forecast

Archived

Jan 22nd, 2024–Jan 23rd, 2024

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

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

Avalanche activity up to size 2.5 continues to be observed - if you're watching the MIN, you can see the hazard building: a bit more triggering each day, two weak layers in the upper snowpack producing test results, and slightly larger avalanches each day. This is a snow and steady pattern of incrementally building avalanche hazard.

Confidence

Low

Avalanche Summary

Avalanche control today on Mt Whymper produced several avalanches to size 2.5 starting at 2700 m and running to the top of the runout zones. These were 20-40 cm windslabs that ran further than expected in the loose surface snow. Control in the Simpson area produced several size 2 avalanches at 2200m, failing 40 cm down on surface hoar and propagating 50-70 meters wide.

Snowpack Summary

The upper 30-50 cm of the snowpack is tricky. Two weak layers buried down about 15 and 40 cm produce test results across the region as the overlying slab is failing and propagating. This slab will continue to develop with Tuesday's wind and warming, and human triggering is expected. The lower part of the snowpack has weak facets and depth hoar and widespread whumphing has been observed in many locations.

Monday's snow profile from Simpson.

Weather Summary

What a change from a week ago, as the storm track now crosses our area bringing light snow, warming temperatures and strong winds. Typical Chinook pattern where the eastern side of the park will be windy (extreme winds on Tuesday) and snow/rain to the west. Expect up to 5 cm over the day on Tuesday with valley bottom temperatures reaching +3 and freezing levels up to 1800 m.

Terrain and Travel Advice

If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

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.

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.