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Avalanche Forecast

Archived

Mar 19th, 2024–Mar 20th, 2024

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
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, human triggered possible.

Regions

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

A major change in weather patterns on Tuesday night as a cold front from NE Alberta moves over the region bringing upslope snow starting Wednesday. If the forecast plays out, 25 cm of cold snow, generally light winds and -12 by Friday will give a full reset to the snow conditions. Switch your avalanche mindset back to winter.

Confidence

Moderate

Avalanche Summary

No significant new avalanches were reported or observed today, and both ski areas reported a reduction in avalanche activity associated with a strong overnight freeze and then cooler daytime temperatures.

Snowpack Summary

The heat wave has produced surface crusts on all aspects except due north above 2100 m, and this layer of crust/wet snow is about to get buried (Mar 20 layer). Initially, pay close attention to the bond between the incoming new snow, and the March 20 layer. We expect avalanches on this crust and their size will depend on how much snow falls. Expect a poor bond initially. Deeper in the snowpack, we expect the cooling trend will strengthen the deeper weak layers (Feb 3).

Weather Summary

Weather changes start tonight as a cold front moves over the area from the NE (upslope) direction. Temperatures will cool progressively through Friday and up to 25 cm of snow is expected by the end of the day on Thursday.

It starts with 5-10 cm on Wednesday, then Thursday is the big day for snow, with up to 20 cm expected throughout the day. Winds will generally be light to moderate and temps will reach -12 by Friday.

Terrain and Travel Advice

  • Closely monitor how the new snow is bonding to the crust.

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.

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.