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Avalanche Forecast

Archived

Jan 18th, 2013–Jan 19th, 2013

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

Regions

Northwest Coastal.

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Only trace amounts of new snow (possibly higher amounts on Monday in the North) are expected for the forecast period. Winds should remain mainly light to moderate from the southwest with freezing levels hovering between 800-900m.

Avalanche Summary

Due to inclement weather observations have been very limited; however, numerous moist or wet snow avalanches to size 2.5 were reported from the region on all aspects at treeline and below. On Thursday numerous avalanches ran to size 3.5 in the north of the region where recent snow accumulations were the highest. They occurred in response to heavy snowfall and strong to extreme winds.

Snowpack Summary

Rain below treeline has maintained moist snow at lower elevations, although a nightly crust recovery is likely with forecast clear skies.  Light amounts of new snow (moderate to heavy amounts in the north) exist as new storm slabs and windslabs at treeline and above. A persistent weakness of surface hoar or facetted snow buried at the end of December sits below all of the more recent storm snow and is still on the radar of professionals in the area. The mid and lower snowpack is generally well settled and strong, although well developed basal facets remain a concern in shallow snowpack areas.

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 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.

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.