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Avalanche Forecast

Archived

Dec 27th, 2019–Dec 30th, 2019

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

Regions

Waterton Lakes.

Natural activity has tapered off but the potential for large avalanches running to the valley bottom remains. These could be triggered by cornices, small avalanches or humans in the wrong spot.

Weather Forecast

Saturday- Sunny with cloudy periods. West  wind 20-40km/h with gusts up to 60km/h.  Freezing Level valley bottom.

Sunday-  Flurries throughout the day. 1-5 cm of accumulation. Freezing Level 1300m. Moderate West -SW winds

Monday-  A mix of Sun and Cloud. Freezing Level valley bottom. Moderate West winds.

Snowpack Summary

The snowpack is thin below 1800m and capped by a met freeze crust. Above 1800m, 85-120cm of snow from last weeks storm sits on top of a weak facet/crust combo. The front ranges hold a thinner, more wind affected, snowpack.

Avalanche Summary

A widespread natural cycle occurred last weekend, with avalanches to size 2 in the storm snow and some larger ones failing on deep persistent weak layers. A size 3 natural avalanche occurred on Mt Bertha Sunday Dec 22 covering the Bertha Falls trail in debris, and a similar avalanche was seen on Mt. Crandell.

Confidence

Due to the number of field observations

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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.