Avalanche Forecast

Issued: Jan 22nd, 2019 4:35PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Storm Slabs.

dsaly, Avalanche Canada

Lizard-Flathead.

Reactive surface hoar, under 10-30 cm recent snow, is most prevalent around treeline and sheltered alpine areas. Avalanches failing on this layer have relatively thin crowns, but may propagate further than expected.

Summary

Confidence

Moderate - Freezing levels are uncertain on Friday

Weather Forecast

TUESDAY NIGHT: Flurries, trace to 10 cm accumulating by Wednesday morning. Moderate southwest wind, freezing level valley bottom.WEDNESDAY: Flurries, trace to 5 cm. Moderate west-southwest wind. Alpine high -4C, freezing level valley bottom.THURSDAY: Mostly cloudy with isolated flurries, trace accumulation. Moderate west wind. Alpine high -6, freezing level rising to 1500 m.FRIDAY: Mainly cloudy. Light northwest wind gusting moderate. Alpine high -1C, freezing level rising above 1500 m.

Avalanche Summary

New snow was reactive on Sunday with several reports of skier-triggered, cornice-triggered, and natural avalanches. On Monday, explosives triggered size 2 storm slab avalanches and cornices. A weak layer of surface hoar buried 10-30 cm is responsible, especially around treeline 1500-1900 m. Most storm slab avalanches are reported on north-northeast aspects 1700-2000 m. However 2 recent avalanches occurred on southerly aspects. On Sunday, a size 2 avalanche released naturally around 2000 m on a southeast aspect with solar input with surprising propagation. On Monday, a snowboarder 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 over a week ago. One was triggered on a thin, rocky, southwest facing feature near ridge crest north of Fernie (report here). The other was triggered on a wind affected south facing slope at treeline in the Corbin area (report here). Deep persistent slab activity has been most common in parts of the region with shallow snowpacks (such as near the continental divide) and alpine features with thin variable snowpack depths.

Snowpack Summary

Flurries with strong winds overnight adds to recent snowfall accumulation totaling 10-30 cm. In the alpine and treeline areas, winds are redistributing storm snow loading lee terrain features and building cornices. The recent snow is sitting over a reactive layer of surface hoar and sun crusts. The surface hoar is most prominent around treeline elevations (1500-1900 m) and sheltered alpine areas. On solar aspects and below treeline, the surface hoar sits on a temperature crust.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

Touchy surface hoar is buried under 10-30 cm recent snow, with deposits up to 50 cm deep in wind-loaded areas. This layer occurs with a crust on solar aspects and most prevalent between 1500-1900 m and sheltered alpine terrain.

Use caution on open slopes and convex rolls at treeline where buried surface hoar may be preserved.Watch for signs of instability such as whumpfing, or cracking. Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Jan 23rd, 2019 2:00PM