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Archived

Avalanche Forecast

Nov 30th, 2021–Dec 1st, 2021
Alpine
5: Extreme
The avalanche danger rating in the alpine will be extreme
Treeline
5: Extreme
The avalanche danger rating at treeline will be extreme
Below Treeline
5: Extreme
The avalanche danger rating below treeline will be extreme
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Banff Yoho Kootenay.

A significant storm is expected on Wednesday. It will be best to enjoy the ski hill and avoid all avalanche terrain.

Weather Forecast

Wednesday will be a crux day for avalanche conditions. 40-100 cm of snow is forecasted by end of day (more snow along the divide). This snow will be accompanied by very strong winds, high freezing levels and rain at lower elevations. Thursday will see convective flurries and clearing skies overnight. Freezing levels will drop to valley bottoms.

Snowpack Summary

30-60 cm recent storm snow is reacting as a storm slab in alpine and tree-line locations. A crust (Nov 15) exists in the mid-pack in most areas below 2100 m. The Nov 5 crust/facet layer exists near the ground. Snowpack depths at tree-line average 80-110 cm. Lower elevation snow (below ~ 1600 m ) is rain- soaked and isothermal.

Avalanche Summary

Natural and explosive triggered  storm slabs  have been observed at tree-line and alpine locations in past 48 hours. Many upper elevation storm slabs are stepping down to the deep persistent layer making for large class three avalanches. At lower elevations (below 1700 m) debris is gouging into isothermal snow and again making for large avalanches.

Confidence

Avalanche Problems

Storm Slabs

40-100 cm of new snow and strong winds will create storm slabs at all elevations.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely - Certain

Expected Size: 2 - 3

Deep Persistent Slabs

With a significant new snow load we expect to see larger and more frequent avalanches occur on the basal crust and facets. These avalanches have potential to run full path.

  • Be aware of the potential for full depth avalanches due to deeply buried weak layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely - Certain

Expected Size: 2 - 3.5

Loose Dry

Significant storm snow on Wednesday will create wide spread loose snow avalanches at all elevations.

Rain and warm temperatures below 2000m has potential to create loose moist avalanches as well.

  • Use extra caution on slopes if the snow is moist or wet.
  • Be careful of loose dry sluffing in steep, confined or exposed terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely - Certain

Expected Size: 1 - 2.5