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Avalanche Forecast

Archived

Feb 22nd, 2024–Feb 23rd, 2024

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

Regions

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

Westerly winds, and small inputs of snow, will contribute to ongoing slab development through Friday.

Expect the hazard to rise through the weekend as a reasonably vigorous weather system brings snow - though amounts seem less certain east of the divide. Slab development can be expected at the upper elevations.

Confidence

Moderate

Avalanche Summary

Sunshine patrol reported triggering very small wind slabs that were 10cm deep.

Lake Louise and Visitor Safety staff travelled parts of the Pumpkin Traverse Thursday and reported ongoing wind transport, wind effect and triggered 2 size 1 slabs 10-20 cm deep on a crust in W facing alpine terrain.

Wednesday, a skier triggered a size 1 slab on the far skiers right on the Surprise Pass ski run. It was 30cm deep and 8m wide and ran for 30m at 2350m and was reported to have failed on facets

Snowpack Summary

5-10cm of snow has come in over the last two days. Sun crusts and moist snow have been found on steep solar slopes while isolated wind slabs can be found in the high alpine. All of this sits on 10-15 cm of facetted snow over the Feb 3 crust that exists on all but N aspects above 2500m. Below this, weak facet layers can be found in the mid and lower snowpack. Generally, thin snowpack values for this time of the year: range is from 80 to 120cm at 2000m.

Weather Summary

A moderate to strong, moist, westerly flow continues. Trace accumulations are expected as freezing levels fall from 1800m to valley bottom overnight Thursday.

Friday, a low pressure system will affect the area by mid-afternoon. 5-10 cm of snow can be expected through Saturday with the potential for larger amounts on west-facing slopes. Moderate to strong westerly winds

For more information see AvCan's Mt Wx Fx.

Terrain and Travel Advice

  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • Watch for signs of slab formation throughout the day.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

Problems

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.

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.