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Avalanche Forecast

Archived

Jan 30th, 2025–Jan 31st, 2025

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

Finally a change to the weather. After a very dry January (17 cm total at Bow Summit), the pattern has shifted and we expect 10-20 cm of new snow and strong winds through Saturday. Avalanche danger will rise quickly as the bond between new and old snow will be poor. Ice climbers: small avalanches may run further than expected in gullies.

Confidence

Moderate

Avalanche Summary

No new slab avalanches were observed or reported on Thursday, but the storm was starting and visibility was limited. Our field team reported a lot of loose dry snow (spindrift) blowing around in the cliff and numerous dry loose sluffs starting to run.

Snowpack Summary

5-20 cm of new snow and strong winds will create surface slabs that bond poorly to the underlying snow. The layer being buried on Jan 30 is a mix of crust, surface hoar and facets - none of which will bond well to the new snow. We expect avalanches to begin failing early in the storm with minimal accumulation. The snowpack is generally weak, with an old crust and depth hoar at the base, so any avalanches starting in the surface layers may step down to the ground and become larger.

Weather Summary

The weather pattern has changed significantly (finally), and there's now a strong onshore flow of moist Pacific air colliding with cold Arctic air. This combination will produce snow. We expect 5-10 cm through the day on Friday, possibly up to 15 cm. Temperatures will be steady around -12 and winds will be strong from the northwest. The storm ends on Saturday and -25 arrives on Sunday night.

Terrain and Travel Advice

  • Storm slab size and sensitivity to triggering will likely increase through the day.

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.

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.

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.