Avalanche Forecast

Archived

Apr 19th, 2012–Apr 20th, 2012

Alpine

Natural avalanches possible, human triggered probable.

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.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Regions

Sea To Sky.

Confidence

Fair - Intensity of incoming weather is uncertain on Friday

Weather Forecast

FRIDAY: Thursday night into Friday may have brought 10-15cm of precipitation. Light to moderate precipitation in the early part of the day on Friday. Strong southwesterly winds and a freezing level of 1300m. SATURDAY: A ridge of high pressure brings mainly dry conditions and warmer temperatures. Winds light southwesterly and freezing levels up to 2000m. SUNDAY: The high pressure prevails but freezing levels rise to 2500m.

Avalanche Summary

Recent observations include cornice falls (size 1-2). Loose moist avalanches have been observed during periods of warming along with thin windslabs (10-20cm deep) above releasing to size 1.

Snowpack Summary

A generally strong and deep spring snowpack exists. At this time of year, snowpack stability tends to decrease during times of warming (e.g. on slopes receiving sunshine, during rainfall, in the afternoon and at low elevations) and improve when the surface freezes. Conditions may be quite icy in the morning. A crust layer from late March, buried within the upper 2 m of the snowpack, remains a lingering concern, although the snowpack above it is settling and strengthening. Large cornices threaten slopes and glide slab releases are a possibility, especially in steep rocky terrain.

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.

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.

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.