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Avalanche Forecast

Archived

Mar 21st, 2012–Mar 22nd, 2012

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, 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 Inland.

The avalanche danger will rise during the day if the forecast for strong solar radiation holds true.

Confidence

Fair - Due to limited field observations

Weather Forecast

Thursday: A mix of sun and cloudy with a chance of flurries - 2-5cm. The freezing level should rise to 800m during the day. Winds are moderate from the southeast. Friday and Saturday: A ridge of high pressure builds in giving drier and sunnier conditions. The freezing level bounces from valley bottom overnight to around 1000m during the day. Winds are generally light from the south.

Avalanche Summary

No new slab avalanches have been reported in the past day or two, although observations were quite limited on Tuesday. There were a few reports of cornice failures on the weekend, but most did not trigger slabs.

Snowpack Summary

Up to 25cm of new snow covers the previous surface which included a sun crust on southerly aspects, surface facets or surface hoar in cool shady areas, and pockets of wind slab in exposed terrain. Moderate southerly winds have created new wind slabs in lee and cross-loaded terrain. The mid February persistent weak layer interface, comprised of spotty surface hoar, facets and crusts, is buried 80-120 cm below the surface. No recent activity has been reported on this interface. However, recent snowpack tests have been giving hard but sudden "pop" results and indicate it is has the potential to react given the right trigger in the right place. For route selection, it should still be on your radar and is more likely to be triggered on steeper, unsupported terrain. Cornices in the area are reported to be very large and primed for natural collapse or triggering by a person.

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.

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.

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.