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Avalanche Forecast

Archived

Dec 29th, 2016–Dec 30th, 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 possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.

Regions

Little Yoho.

We are in a storm period and expect natural avalanches running over the next 24-48 hours. Ice climbers in Field should avoid the big gully climbs over the next few days and let this new snow settle. Skiers - wind slabs are primed for triggering.

Weather Forecast

Strong westerly flow continues but the main pulse of snowfall should taper by Friday morning. Friday looks like a mix of sun and clouds with winds tapering slightly and temperatures remaining cool (below -10). Another round of snow is expected for Saturday.

Snowpack Summary

At 1850 m. 40 cm of settled storm snow sits on the Dec 19 layer of facets and produces moderate (PC) compression test results. Another profile at 2100 m. showed no shears in the snowpack. At the higher elevations, strong winds over the past week have created widespread wind slabs which will be easily triggered by people.

Avalanche Summary

Poor visibility today, but the ski areas reported only small soft slabs within the recent snow inside the ski area boundary.

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.