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Avalanche Forecast

Archived

Feb 5th, 2016–Feb 6th, 2016

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

Regions

Little Yoho.

We expect a natural avalanche cycle to occur in the alpine overnight Friday and into Saturday. Minimize your exposure to large alpine slopes and watch for small wind loaded slopes at lower elevations.

Weather Forecast

10-20cm of snow is forecast for Saturday in most areas with very strong alpine winds out of the West. Temperatures will gradually drop into the -10 to -15'C range as the weather begins to clear late on Saturday. Light flurries and moderate West winds are expected for Sunday.

Snowpack Summary

New wind slabs forming in the alpine and tree line areas which are easy to trigger. The Jan 6 surface hoar/facet/sun crust layer, down 30-60cm, is becoming less reactive to skier triggering, however sudden collapse results persist on the Jan 6 and Dec 3 layers. Isolated whumphing on mid-pack facets/surface hoar have been observed this past week.

Avalanche Summary

Several new natural wind slab failures were observed Friday up to size 2 in the Lake Louise area as the winds began to increase and the temperatures warmed up. We expect a substantial increase in natural activity over the next 24 hours as the storm arrives.

Confidence

Forecast snowfall amounts are uncertain on Saturday

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.

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.

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.