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Avalanche Forecast

Archived

Apr 7th, 2013–Apr 8th, 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 possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Sea To Sky.

Confidence

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

Weather Forecast

Synopsis: A brief ridge of high pressure will result in drier conditions and sunny breaks on Monday. The next system arrives sometime on Tuesday bringing moderate precipitation through Wednesday. Monday: Cloudy with sunny breaks. The daytime freezing level rises to around 1500 m. Winds are light from the northwest. Tuesday: Increasing cloud with precipitation developing in the afternoon (~10-15 cm). The freezing level is around 1300-1500 m. Winds increase to moderate or strong from the southwest. Wednesday: Moderate precipitation continues. The freezing level is steady between 1300 and 1500 m.

Avalanche Summary

Numerous size 1-2 slab avalanches were released with explosive control on Saturday. Most of these avalanches occurred in the alpine and failed at the base of the recent storm snow on a melt-freeze crust. One event was reported to be a size 2.5 and may have released in wet snow below the crust.

Snowpack Summary

Recent snowfall amounts vary considerably with elevation due to fluctuating freezing levels. Some lee alpine areas may have accumulations over 50 cm. Dense new wind slabs are likely in exposed lee terrain at and above treeline. Most of the recent precipitation fell as rain or wet snow below 1700-1800 m. The upper snowpack at lower elevations has become isothermal from recent warm temperatures and rain.Cornices are very large and could pop off with continued mild temperatures or during periods of sun.

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.