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Avalanche Forecast

Archived

Dec 27th, 2012–Dec 28th, 2012

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

Regions

South Rockies.

Confidence

Good

Weather Forecast

Friday: Northwesterly flow tapers off overnight as an upper ridge moves across the region. Cloudy skies and a trace of new snow. Ridgetop winds will be moderate-strong blowing from the W-NW. Treeline temperatures near -9. Freezing levels will remain in the valley bottom through the forecast period.Saturday:  Upper ridge moves across the region bringing cloudy skies, light snow amounts and moderate West winds at ridgeline. Treeline temperatures near -6.Sunday: Mainly dry, cooler conditions.

Avalanche Summary

Last Sunday afternoon, skiers triggered a size 3.0 slab avalanche from the ridgeline off Mt. Fernie. The initial trigger was a smaller wind slab which then stepped down to a deeply buried rain crust. There were no human involvements. For further details, please visit the Incident report here:  https://avalanche.ca/cac/library/incident-report-database/view.No new avalanche observations reported on Thursday.

Snowpack Summary

Recent storm snow is starting to settle out and bond within the upper snowpack. Moderate to strong winds from the SW-NE have built wind slabs that may be sensitive to rider triggers. Likely areas where a wind slab problem may exist are: lee slopes and behind terrain features (spines, gullies, ridgelines). Two crusts have been identified in the snowpack: one close to the ground that formed in early November down 170-200 cm and one around 90-140 cm below the surface, which formed in early December. Recent snowpack tests done on the December crust from the Harvey Pass Riding Area showed a moderate compression test failure, with a sudden collapse characteristic. The testing done on that layer showed inconsistent results. Recent compression and deep tap tests done in the Lizard Range have shown hard results. This layer may be difficult to trigger, especially in deeper snowpack areas. However, if triggered, a large and destructive avalanche would occur. Typical trigger points are thin-thick snowpack areas, cross loaded gullies or around rocky outcrops. The mid pack is generally well settled throughout the region.

Problems

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.