Avalanche Forecast

Archived

Feb 25th, 2024–Feb 26th, 2024

Alpine

Natural and human triggered avalanches likely.

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, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

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

The danger has risen due to 15-35cm of new snow and strong winds. Winds will die off on Monday, and the natural cycle should taper. Conditions will remain ripe for human triggering.

Confidence

Moderate

Avalanche Summary

There have been plenty of reports over the past 24 hours of natural and skier and climber triggered avalanches to size 2.5. This includes a partial burial of 2 people on Mt. Whymper's North side.

A natural cornice fall in the Southside chutes (out of bounds) triggered a slab on the February 3rd crust (size 2.5). Otherwise, the ski hills reported smaller avalanches (sz. 1) with explosives within the new snow.

Snowpack Summary

15-35cm HST and strong winds have formed widespread slab formation at treeline and above, and storm slabs below treeline. 25-50cm+ overlies the Feb 3 crust and facets, which is 0.5-15cm thick and exists up to 2500m (higher on solar aspects). In shallower snowpack areas, weak facet layers can be found in the mid and lower snowpack. Snowpack depths are low this year, with about 80-120cm at treeline.

Weather Summary

Monday - trace amounts of snow in the East and up to 5cm along the divide. Winds will be light from the NE, switching to SW in the PM. A cooling trend will start.

Tuesday - Trace amounts of snow, a mix of sun and cloud, and light West winds with temperatures of -15 to -20C in the AM

Wednesday - 5cm of snow as another system approaches with a warming trend and moderate SW winds

For more information, see AvCan's Mt Wx.

Terrain and Travel Advice

Watch for signs of slab formation throughout the day.
If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.