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Avalanche Forecast

Archived

Mar 8th, 2013–Mar 9th, 2013

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

Regions

Sea To Sky.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain on Sunday

Weather Forecast

A ridge of high pressure should persist for one more day bringing mainly clear skies for Saturday. Winds are expected to be light and northwesterly with the freezing level at 1900m.The ridge then flattens and a more zonal pattern is forecast to bring snowfall and seasonal temperatures to the region for Sunday and Monday. At this point there is significant model disagreement with the timing and intensity of this next system.

Avalanche Summary

Size 1 loose wet avalanches were reported from the region occurring in steep, south-facing terrain. With forecast warming on Saturday, I would expect ongoing wet snow instabilities with the potential to trigger deeper persistent weaknesses in isolated terrain.

Snowpack Summary

Light snowfall overlies wind slabs in exposed areas, surface hoar or facets in sheltered locations, or a sun crust on south facing terrain.Below the surface, last week's accumulations of 70-120cm continue to settle and strengthen. A weakness of surface hoar and/or a crust exists near the base of the storm snow (now 1-2 m deep in some locations). This layer was the culprit in most of the large avalanches that occurred last weekend. This layer could still be triggered in shallow rocky areas or by large triggers like a cornice fall. I would suggest avoiding any large slope that did not release during the latest avalanche cycle, especially with forecast solar warming on Saturday. Below this interface, the snowpack is strong and well settled.

Problems

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.