Avalanche Forecast

Archived

Mar 26th, 2025–Mar 27th, 2025

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural and human triggered avalanches likely.

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Regions

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

A major avalanche cycle occurred on Wednesday, and this will continue on Thursday. Natural avalanches ran over the ice climbs Masseys and Guinness Gully near Field, as well as 75% of the avalanche paths in the Kootenay highway and reports of widespread activity in Bryant Creek. Avoid all avalanche terrain on Thursday.

Confidence

High

Avalanche Summary

A widespread avalanche cycle occurred starting midday on Wednesday, with avalanches starting at all elevations and numerous paths running to the valley bottom. Masseys ice climb ran mid-day, burying half of the first pitch, as well as all of the ice climbs on Mt Dennis, including Guiness Gully. Widespread avalanche activity was also reported in Bryant Creek and in the Mt. Assiniboine area. Expect this condition to have been everywhere in our region.

Snowpack Summary

15 cm of new snow and/or 13 mm of rain has fallen in the past 24 hours, up to 2200 m in the region, triggering a widespread avalanche cycle and causing dramatic snowpack settlement (see images). A dense slab 50-100 cm thick overlies a weak, facetted snowpack which is now isothermal below treeline. Natural and human triggered avalanches are almost certain in all areas.

Weather Summary

In the wake of Wednesday's warm front, another push of snow and rain will cross the region on Thursday, with 20-40 cm of snow expected and freezing levels at 2200 m, but on a cooling trend. This will result in rain below treeline, mixed snow and rain at treeline, and new snow in the alpine. Winds look to be in the moderate range.

Terrain and Travel Advice

Avoid the runout zones of avalanche paths. Avalanches could run full path.
A moist or wet snow surface, pinwheeling, and natural avalanches are all indicators of a weakening snowpack.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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.

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.