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Avalanche Forecast

Archived

Feb 29th, 2024–Mar 1st, 2024

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.
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.

Avoid all avalanche terrain and overhead hazard.

Large natural avalanches or user-triggered avalanches remain very likely.

Special Avalanche Warning effect, click on the red banner above.

Mt. Field and Sunshine Road avalanche closure zones are CLOSED on Friday, March 1st.

Confidence

High

Avalanche Summary

A major avalanche cycle occurred Thursday. Large natural & human-triggered avalanches will remain very likely on Friday. Avoid all avalanche terrain and runouts.

Heavy snowfall and no visibility on Thursday. Avalanche control on Mt Whymper (Kootenay NP) on Tuesday and today on Bosworth produced size 2-3 avalanches with every shot. The crowns were 40-100 cm deep and the failure plane was the Feb. 3rd crust and occasionally stepping down to ground.

Snowpack Summary

Extensive wind slabs formation on lee aspects at ridgetop. 60-90 cm of recent snow sits on top of the Feb 3rd crust/ facet layer. This crust is variable in thickness and exists up to 2500m (higher on solar aspects). In thinner eastern areas, the mid and lower snowpack are weak and facetted.

Average snowpack depths at treeline range from 80 cm in thinner eastern areas to 180 cm in thicker western areas.

Weather Summary

Thursday Night: trace amounts in the wake of Thursday's storm. Winds will taper to light and temperatures will drop to -13C

Friday: Mix of sun and cloud. Light winds in the morning, may increase to 30 km/hr in the afternoon. Alpine high -11C

Saturday: Scattered flurries with moderate southerly ridgetop winds. Alpine high -13C

Click here for a more detailed weather forecast

Terrain and Travel Advice

  • Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • 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.

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.