Avalanche Forecast

Archived

Mar 7th, 2018–Mar 8th, 2018

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

South Coast.

Avalanche danger will increase as snow accumulates at higher elevations.

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Thursday

Weather Forecast

THURSDAY: Precipitation starting Wednesday night with 5 mm by the morning and another 10-20 mm possible by Thursday afternoon. Freezing level will be steady around 1300 m so expect a mix of rain and snow at treeline elevations. Moderate south wind.FRIDAY: Flurries continue over Thursday night and into Friday bring 10-20 cm of snow by the morning, clearing in the afternoon, light wind, freezing level dropping to around 800 m.SATURDAY: Mostly sunny, light wind, freezing level rising to around 1600 m.

Avalanche Summary

No recent avalanches have been reported.A MIN report from just outside the region near Squamish on Sunday (Watersprite Lake) describes a natural size 2 avalanche that failed on a south aspect at 1750 m (see photo and details here). Sparse observations from the Squamish area over the past week suggest the snow from last week's storm may still be unsettled in that area.

Snowpack Summary

New snow will accumulate on Thursday and Friday and form extra deep deposits in wind loaded terrain. The new snow is falling on a sun crust on steep south-facing slopes, cold dry snow on polar aspects, and an overall well settled snowpack.Cornices have formed on many alpine ridgelines. They will become touchier as they grow in size, as temperatures rise, and as they are subject to the strong late-winter sun on clear days.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.