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Avalanche Forecast

Archived

Dec 12th, 2013–Dec 13th, 2013

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

Regions

South Columbia.

Confidence

Fair - Intensity of incoming weather systems is uncertain on Saturday

Weather Forecast

Friday: Light flurries / Light southwest winds / Freezing level at 1100mSaturday: Light to moderate snowfall / Strong West winds / Freezing level at 1100mSunday: Light to moderate snowfall / Moderate southwest winds / Freezing level at 1300m

Avalanche Summary

Ongoing low density surface sluffs to size 1.5 at treeline and below have been reported from the region. A few recent natural windslabs to size 2 have also been reported in north-facing alpine terrain. Recent weather has likely kept observation to a minimum. I would expect to hear more about recent avalanche activity with the forecast break in the weather on Friday.

Snowpack Summary

Moderate to locally heavy amounts of low density snow now overlie generally faceted surfaces that formed during the recent cold snap. At the same buried interface you may find small surface hoar on sheltered slopes or windslabs in exposed terrain. On sheltered, lower elevation slopes the new snow is mostly unconsolidated; however, moderate to strong southwest winds have created wind slabs in exposed high elevation terrain.Professionals are still keeping their eye on the late-November interface (about 40-80cm below the surface) which consists of sun crusts on steep south facing slopes and surface hoar in sheltered areas. This layer is still producing sudden test results, and may be triggered with nasty consequences on steeper, unsupported terrain. At the base of the snowpack is a crust/facet combo that formed in October. About 60cm above the ground is a surface hoar layer which formed in early November. These layers have become generally inactive; however, residual risk of large, destructive avalanches exists, especially in areas with a thinner snowpack.

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.