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Avalanche Forecast

Archived

Feb 2nd, 2017–Feb 3rd, 2017

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

Regions

Purcells.

Touchy winds slabs are lurking below ridgecrests and behind terrain features. Use extra caution as you transition into wind affected terrain and watch for signs of recent wind loading.

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

FRIDAY: Increasing cloudiness with light snow flurries starting in the afternoon/evening. Light but gusty southwesterly winds and freezing levels remaining in valley bottoms with alpine temperatures reaching -10 C.SATURDAY: Cloudy with flurries bringing  5-10cm under light but gusty southwesterly winds. Freezing levels remaining in valley bottoms with alpine temperatures reaching -10 C.SUNDAY: Cloudy with flurries bringing  5-10cm under moderate southwesterly winds. Freezing levels remaining in valley bottoms with alpine temperatures reaching -10 C.

Avalanche Summary

On Monday, several natural wind slab avalanches up to size 2 were observed throughout the region. These avalanches occurred on most aspects and were mainly in the alpine. Since then, skiers and sledders have been triggering several wind slab avalanches up to size 1.5. A MIN report from the Quartz Creek area shows a sledder triggered size 2 wind slab avalanche. Click here for more details. Fresh wind slabs are expected to remain sensitive to human triggering, especially on steep and unsupported (convex) slopes. Winds have recently switched from south to north and wind slabs should be expected on all aspects in exposed terrain.

Snowpack Summary

5-20cm of recent snow with strong shifting winds (including down-slope "katabatic" winds) have resulted in touchy wind slabs on a variety of aspects in wind exposed terrain. A sun crust is being reported on steep sun-exposed slopes and small surface hoar has been growing on sheltered open slopes. Surface faceting is also being reported as a result of the current cold temperatures. A persistent weakness buried mid January is now down 20-50 cm and consists of buried surface hoar in sheltered areas, sun crust on south aspects, and/or widespread faceted old snow. It has generally stabilized but may be sensitive to triggering in isolated areas where buried surface hoar is preserved. Another surface hoar/facet persistent weakness buried mid-December may be found down 50-100 cm, but is generally considered dormant. This and deeper persistent weaknesses remain an isolated concern in shallow snowpack areas where the weakness is closer to the snow surface.

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.