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Avalanche Forecast

Archived

Mar 27th, 2013–Mar 28th, 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 unlikely, human triggered possible.
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

Northwest Coastal.

Confidence

Good

Weather Forecast

Thursday: Expect few clouds with light westerly winds and alpine temperatures reaching -2.Friday & Saturday: The pattern continues, with mostly sunny skies, light westerly winds and alpine temperatures climbing to -1 in the afternoons.

Avalanche Summary

Natural and rider triggered avalanches up to 2.5 have been reported, likely triggering on the March 9th layer. Loose wet sluffs up to 2.0 have also been reported

Snowpack Summary

Recent new snow is settling with the influence of warm temperatures. Solar aspects now sport a melt freeze crust. Wind slabs may be found at alpine and treeline elevations on many slope aspects due to variable winds. A layer of surface hoar (buried March 9th; now down about 40-60 cm) is slowly becoming less touchy, but professionals are keeping a wary eye on it. In some places this interface is a crust/facet layer. Triggering this layer is becoming a low probability but high consequence problem. Check out the?Forecaster's Blog?for related discussion. A second surface hoar layer, buried on March 18, is also reported to be gaining strength. The mid snowpack is generally well settled and strong. Cornices are large and untrustworthy, especially when the sun is out.

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 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.