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Avalanche Forecast

Archived

Mar 12th, 2024–Mar 13th, 2024

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.
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.

This is a condition that is slow to heal. Although the natural cycle is mostly over, the persistent slabs still lurk. The only way to manage the conditions is with terrain choices.

Confidence

High

Avalanche Summary

The forecasting field team did not observe any new avalanches in the Mt. Field area today. Sunshine patrol reported triggering one size 1 persistent slab with explosives.

Snowpack Summary

15-20 cm of storm snow overlays previous wind slabs (alpine and treeline), temp crusts at lower elevations, and sun crusts on steep solar aspect. 40-80 cm of settled snow overlies weak facets above the Feb 3 crust interface which exists up to 2500 m, (higher on solar aspects). Many recent avalanches have been running on this layer. The base of the snowpack consists of weak facets. Deeper snowpack areas (west of the divide) are more settled and stronger.

Weather Summary

Lingering cloud and trace accumulations of snow is expected on Wednesday. A high-pressure system is building into the region on Thursday. Until then temperatures will be seasonal with -10 at the ridge and -3 in the valley. Winds should be light/moderate from the SW. Very high freezing levels are forecasted for late in the week.

For more detailed weather information, click here.

Terrain and Travel Advice

  • Use conservative route selection and resist venturing out into complex terrain.

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.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.

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.