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Avalanche Forecast

Archived

Mar 15th, 2025–Mar 16th, 2025

Alpine
Natural avalanches possible, human triggered probable.
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.
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 REMAINS VERY LIKELY. Touchy slabs exist over very weak persistent layers.

A widespread natural avalanche cycle has continued all week and natural activity remains possible this weekend

Stick to the basics: Stick to low angle terrain well away from any avalanche terrain or steeper slopes.

Confidence

High

Avalanche Summary

Avalanche accident Friday, outside of Lake Louise Ski Area Boundary. A size 2.5 avalanche was triggered and failed on the deep persistent layer at the ground.

A flight to the Lake O'hara area saw further evidence of a widespread natural cycle that has occurred over the last week. Many long fracture lines were observed with avalanches to sz 3.5 all failing on midpack or deeper layers.

The crown line on a slab at Panorama Ridge measured roughly 2.4km.

Snowpack Summary

40 to 70cm of settled storm snow since March 8th, with the most snow in the Bow Summit region, along the Wapta, and in Little Yoho. Strong S winds have formed slabs over sun crusts on steep S aspects or firm wind-affected snow elsewhere.

A persistent weak layer (Feb 22/Jan 30 facets) is buried 50-100 cm deep. In shallower eastern areas, the mid/lower snowpack is very weak with facets and depth hoar, while deeper western areas are more consolidated (see profiles below).

Weather Summary

Another low-pressure system will impact the forecast region on Sunday, bringing 5 to 10 cm of snow accumulation. Ridgetop winds will increase to strong values from south west, and freezing levels will remain at the valley bottom.

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

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.