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Avalanche Forecast

Archived

Nov 25th, 2021–Nov 26th, 2021

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 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.

Regions

North Rockies.

Large amounts of recent snow (up to 80 cm at Pine Pass) and strong, southwesterly winds have created fresh storm slabs reactive to human triggers. These slabs will be especially reactive on lee features at treeline and above.

Confidence

Low - Uncertainty is due to the limited number of field observations.

Weather Forecast

THURSDAY NIGHT: Snow; 5-10 cm / Strong, southwesterly winds / Low of -7 / Freezing level 1300 m.

FRIDAY: Mostly cloudy with isolated flurries; 0-3 cm. / Strong, southwesterly winds / High of -6 / Freezing level lowering to 700 m.

SATURDAY: Mix of sun and cloud / Strong, southerly winds / High of -3 / Freezing level 1300 m.

SUNDAY: Snow; 15-20 cm / Strong, southwesterly winds / High of 1 / Freezing level 1500 m.

Avalanche Summary

Although no avalanches have been reported, a natural avalanche cycle likely occurred at upper elevations in the Pine Pass area today.

There have been no reports of avalanches on persistent weak layers this season, although reports are limited, and we strongly encourage people to share observations on the Mountain Information Network. 

Snowpack Summary

The Pine Pass area received up to 80 cm of recent snow with strong southwesterly winds and warm temperatures. All of these factors contribute to the formation of fresh storm slabs, especially at treeline and above.

The southern portion of the region received 15-30 cm from the recent storm which combined with the strong southwesterly winds is also enough snow to form fresh storm slabs reactive to human triggers.

Recent observations suggest treeline snow depths are around 80-140 cm with very little snow below 1400 m in much of the region except for the pine pass area which now has enough snow below treeline for avalanching.

  A series of storms over the past few weeks delivered about 40-80 cm of snow, which sits above an early season crust(s). Reports indicate the snow has generally bonded well to the early season crusts. Exceptions may be shallow alpine slopes along the eastern side of the Rockies towards Jasper.

Terrain and Travel

  • Give the new snow time to settle and stabilize before pushing into bigger terrain.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Be especially cautious as you transition into wind affected terrain.
  • Avoid freshly wind loaded terrain features.
  • Remember that the snowpack will be significantly different at higher elevations than lower down.

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.