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Avalanche Forecast

Archived

Dec 23rd, 2015–Dec 26th, 2015

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, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Waterton Lakes.

Don't let powder euphoria override your judgement - think carefully before entering big slopes, or traveling above terrain traps.  Buried wind slabs and a weakening buried crust may both make slopes difficult to evaluate. 

Weather Forecast

An Arctic front slowly slips over us tomorrow, bringing flurries tonight & tomorrow. Most models predict 3 - 5cm of snowfall. Some periods of Moderate W winds at ridges. Already cool temperatures will fall sharply late tomorrow. For Friday, expect an improvement in the weather, and temperatures in the -8 to -14 range. Saturday is looking clear.

Snowpack Summary

Up to 20cm of low density snow has fallen since Dec 20 with Light NE winds, before a period of Moderate NW wind yesterday evening. This has buried wind slabs formed by previous strong SW winds. Below this is the Dec 9th crust (down 40-80cm), which has become a concern as a potential weak layer. Two more crusts exist in a strong lower snowpack.

Avalanche Summary

One large slab avalanche failed naturally within the last 24 hours, on an open slope at Treeline elevation on the Eastern aspect of Mt Rowe. Also, several size 1 loose snow avalanches, both natural and human triggered have been observed over the past two days.

Confidence

Due to the number of field observations

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.

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.