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Avalanche Forecast

Archived

Dec 18th, 2017–Dec 19th, 2017

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 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

Purcells.

Snowfall amounts will continue to gradually accumulate over a variety of potential weak layers in the coming days.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Wednesday

Weather Forecast

TUESDAY: Mainly cloudy with periods of snow in the afternoon and overnight accumulations 10-20cm, wind moderate east, alpine temperature -9WEDNESDAY: Cloudy with sunny breaks and isolated flurries, wind light northeast, alpine temperatures -10THURSDAY: Mainly cloudy with isolated flurries, wind light to moderate northwest, alpine temperature -9 

Avalanche Summary

Recent reports in the north of the region indicate numerous size 1-1.5 wind slab and loose snow avalanches in the alpine and tree line over the past few days. As snow amounts continue to accumulate and settle in the coming days, expect to see an increase in avalanche activity. Please submit any observations you may have to the Mountain Information Network (MIN).

Snowpack Summary

15-25cm of new snow accumulating through the weekend now sits on a wide variety of old surfaces including large surface hoar (weak, feather-like crystals), hard crusts formed by sun or wind, and sugary facets. As the snow load builds and slab properties develop, it will be important to monitor how the new snow is bonding to the old surfaces. Most concerning would be areas that have surface hoar sitting on top of a hard crust. A crust which was formed by rain in late November is a major feature in the snowpack and is down approximately 40-60cm at tree line elevations. Snowpack tests suggest the snow above is currently bonding well to it.Snowpack depth decreases rapidly below tree line. Look out for early season hazards such as rocks, stumps, and open creeks.

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.