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Avalanche Forecast

Archived

Jan 27th, 2016–Jan 30th, 2016

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

Regions

Waterton Lakes.

The potential for buried persistent weak layers to have created a low probability/high consequence avalanche problem makes for decreased confidence.  Evaluate the snowpack and terrain carefully before exposing yourself to larger features.

Weather Forecast

Ongoing chinook winds (strong to extreme from the west) and warm temperatures (highs of 10 deg for the townsite and freezing levels as high as 2100m) will begin to abate Thursday afternoon, as the trailing end of a cold front brings increasing cloudiness, cooling temperatures and light precipitation to the area through Friday.

Snowpack Summary

Strong to extreme chinook (westerly) winds continue to build windslabs in lees and windpressed surfaces in exposed areas. These windslabs are stubborn to trigger but may propagate widely if they initiate on/step down to previously buried weak layers; a Jan 4th crust/surface hoar (solar/shady aspects) down 40-70cm, and a Dec 9th crust down 70-120cm.

Avalanche Summary

A few isolated large avalanches were observed locally last weekend, these are suspected to have been persistent slabs failing on the Jan 4 crust/surface hoar layer. Neighboring ski operations have been reporting isolated large persistent slab avalanches failing on the Dec. 9th crust.

Confidence

Freezing levels are uncertain

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 Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.