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Avalanche Forecast

Archived

Feb 4th, 2018–Feb 5th, 2018

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

Jasper.

While we expect natural activity to drop off as recent storm and wind slabs settle out and the cold air takes over, the persistent slab problems still linger. Another storm in the forecast for Wednesday will provide a further test to the snowpack.

Weather Forecast

Warm, wet, pacific air is over-riding the cold arctic air that arrived to Jasper with a NorthWesterly flow Feb 3. A few cm of snow can be expected overnight Sunday before the cold air wins out again yielding a return to clear, mainly calm and cold through Tuesday. Forecasts call for this same pattern to bring another push of Pacific air Wednesday

Snowpack Summary

10-15 cm of new snow arrived with a Northerly flow Saturday. This sits over recent wind and storm slabs formed by 40cm of snow pushed around mainly by strong SW winds. Midpack persistent weak layers, mainly preserved Jan 7surface hoar down 40 to 60cm and the rotten Dec 15 FC sitting just below are still a concern but remain stubborn to triggering.

Avalanche Summary

Avalanche control on Wednesday along the Icefields Parkway produced numerous size 3 avalanches in the alpine, and many size 2-2.5 storm slab and loose avalanches at all elevations. Persistent slab avalanches were produced in the alpine where wind loaded areas provided enough of a load to trigger a step down to these mid-pack layers.

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.

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.