Avalanche Forecast

Archived

Apr 11th, 2012–Apr 12th, 2012

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Regions

Northwest Coastal.

Field observations are limited for this region. Send us yours! [email protected]

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Thursday: A mix and of cloud and light precipitation. Freezing level around 1500 m. Light southerly winds.Friday: Cloud or light precipitation, dissipating. Light winds. Freezing level around 1500 m. Saturday: Clearing skies. Light south-westerly winds. Freezing level 1500 m.

Avalanche Summary

Recent reports include wet loose avalanches up to size 2.5 in response to warming and sunshine. Large glide avalanches were also reported. On Saturday, a size 3 glide release removed trees and left a 4-5 m deep deposit near Shames. Last week, a large icefall triggered a slab in the Bear Pass area, creating a size 4 avalanche.

Snowpack Summary

Cornices and icefall are an increased concern now that spring is upon us. A melt-freeze crust exists on solar aspects and at low elevations. In some areas, limited overnight cooling has kept surface snow from re-freezing, leaving it loose and cohesionless. Forecast rainfall at low elevations may keep the snow surface weak. Pockets of dry snow and surface hoar may still be found on high north aspects. Areas of wind slab formed with recent easterly outflow winds. Glide cracks have opened up and pose the threat of full-depth releases, especially on steep rocky terrain features.

Problems

Wet Slabs

Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.

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.