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Avalanche Forecast

Archived

Jan 21st, 2019–Jan 22nd, 2019

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

Regions

Lizard-Flathead.

Reactive surface hoar, under 10-20 cm recent snow, is most prevalent around treeline and sheltered alpine areas. Recent avalanches have relatively thin crowns, but propagated further than expected. Human triggered avalanches remain possible.

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

MONDAY NIGHT: Cloudy with clear periods. Light to moderate west-southwest wind. Alpine low -13C, freezing level valley bottom.TUESDAY: Mainly cloudy with isolated flurries, trace to 5 cm accumulation. Moderate southwest wind. Alpine high -7C, freezing level valley bottom.WEDNESDAY: Flurries, 10-15 cm accumulation. Moderate west-southwest wind. Alpine high -4C, freezing level climbing to 1100 m.THURSDAY: Mostly cloudy with isolated flurries, trace accumulation. Light to moderate west wind. Alpine high -6, freezing level valley bottom.

Avalanche Summary

New snow was reactive on Sunday with several reports of skier-triggered, cornice-triggered and natural avalanches. A weak layer of surface hoar under the new snow is the likely suspect especially, around treeline elevations 1500-1850 m. Most of these storm slab avalanches are reported on north-north east aspects between 1700-2000m, however 2 recent avalanches occurred on southeast aspects. On Sunday, a size 2 avalanche released naturally around 2000 m with solar input with surprising propagation. And on Monday, skiers triggered a size 2 avalanche on a south aspect in open trees outside the Fernie boundary, fortunately with no injury. Two large snowmobile triggered avalanches were reported last weekend. One was triggered on a thin, rocky, southwest facing feature near ridge crest north of Fernie (see here for report). The other was triggered on a wind affected south facing slope at treeline in the Corbin area (see here for report). Deep persistent slab activity this season has been most common in parts of the region with shallow snowpacks (such as near the continental divide) and on alpine features with thin variable snowpack depths.

Snowpack Summary

10-30 cm recent snow buried a weak layer of surface hoar and sun crusts. Wind has redistributed snow in the alpine and treeline and built cornices. The surface hoar is associated with a crust on solar aspects and is most prominent around treeline elevations (1500-1850 m) and sheltered alpine areas. Below 1500 m, the surface hoar/crust combo is found on all aspects.In shallow snowpack areas, the base of the snowpack may still be composed of weak faceted grains. In deeper snowpack areas, the middle and lower portions of the snowpack are generally considered to be well-settled and strong.

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.