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Avalanche Forecast

Archived

Mar 23rd, 2013–Mar 24th, 2013

Alpine
Natural avalanches possible, human triggered probable.
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

South Rockies.

Confidence

Good

Weather Forecast

Synopsis: Generally very fine weather with cool overnight temperatures and warm, sunny days.Sunday, Monday and Tuesday: Clear and sunny. Freezing level around 1800 m, becoming slightly higher each day. Light winds.

Avalanche Summary

A couple of large natural avalanches were reported from northeast of Sparwood that likely ran on Wednesday or Thursday on the buried rain crust. On Friday, a few cornice releases were observed and sluffing was noted in the new snow on steep terrain.

Snowpack Summary

Approximately 40-70 cm recent storm snow sits on top of a buried rain crust that exists up to around 2100 m. In areas near Sparwood, the new snow initially bonded poorly to this crust, and a few large avalanches were observed that likely released on this layer. In the North Elk Valley, the bond at the crust was reported to be good. Generally, this interface has now become stronger for all parts of the region, and is now considered unlikely to release due to the weight of a person alone. However, a large trigger, such as a cornice fall, or an airborne sledder, could potentially trigger a large avalanche on this layer in steep terrain. Recent wind slabs exist in the immediate lee of ridge lines and terrain features. Cornices are large and fragile. Mid and lower snowpack layers are generally well-settled.

Problems

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.

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.