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Avalanche Forecast

Archived

Mar 12th, 2025–Mar 13th, 2025

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
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.

Human triggering of avalanches is almost certain right now, especially on Hwy 93 north around Bow Summit, where the snowpack almost doubled in 48 hours. Many reports of spooky conditions, whumphs, remote triggers and large avalanches with more snow coming on Thursday. Stay away from avalanche terrain, conditions are dangerous.

Confidence

High

Avalanche Summary

Poor visibility today, but natural avalanche activity continues, with a size 2.5 recorded outside the Sunshine boundary and another size 3 reported in Kananaskis Country. Fracture lines 300 - 500 meters wide. We don't have any reports from teams in the backcountry today. The photo below is from Mt Hector, several days ago but gives a sense of how wide the fracture line are.

Snowpack Summary

The recent storm dropped 25 cm (in Kootenay & Sunshine), 50 cm (Lake Louise), and 75+cm (Bow Summit). Strong southerly wind redistributed this snow creating slabs over suncrusts on steep south aspects or firm wind affected snow elsewhere. A persistent weak facet layer (Feb22/Jan 30 layer) is buried 40-100cm down.

In shallower eastern regions, the mid and lower snowpack is very weak with facets, while deeper western regions are more consolidated.

Weather Summary

The storm track continues this week, as another low-pressure system moves over our region bringing more snow on Thursday. Snow begins Thursday morning and we could see between 10-20 cm by the end of the day. This snow falls under temperatures from -4 to -6, and moderate winds from the SW.

Terrain and Travel Advice

  • Make conservative terrain choices and avoid overhead hazard.
  • Remote triggering is a big concern, be aware of the potential for wide propagations and large, destructive avalanches at all elevations.

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.

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.