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Avalanche Forecast

Archived

Apr 4th, 2017–Apr 5th, 2017

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 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 Coast Inland.

Forecast precipitation amounts and freezing levels vary from the north of the region to the south. Higher than forecast precipitation may lead to locally elevated danger ratings.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Wednesday

Weather Forecast

WEDNESDAY: Mix of rain and snow, accumulation Tuesday night into Wednesday 5-15cm / Moderate south wind / Alpine temperature -2 in the north and 2 in the south / Freezing level 1500 m in the north and 1800m in the southTHURSDAY: Mix of rain or snow, accumulation 5-15cm / moderate to strong south wind / Alpine temperature -2 in the north and 3 in the south / Freezing level 1500 m in the north and 1900m in the southFRIDAY: Cloudy with isolated flurries / Light to moderate southwest wind / Alpine temperature 0 / Freezing level 1500m

Avalanche Summary

A report from Monday indicates a size 2.5 explosives controlled cornice failure stepping down to what was suspected to be a mid-February persistent weak layer in the Duffy Lake area. Another report from the same area indicates a size 3 large explosives triggered avalanche stepping down to what was suspected to be a November persistent weak layer. There was also a social media report from Sunday that describes two skier triggered wind slab avalanches in the Heart Strings area. Click here for details and photos. There have been no new avalanche reports from the Coquihalla area or south of the region in the past several days.On Wednesday, recently formed wind slabs are expected to remain reactive to human triggering. These slabs are expected to be particularly touchy where they overlie a melt-freeze crust.

Snowpack Summary

5-15cm of new snow falling at upper elevations Tuesday night into Wednesday is sitting on a widespread melt-freeze crust on all aspects and elevations except for high elevation north facing terrain. Recent strong winds from the south have formed new wind slabs in the alpine and have added load to cornices. On sun exposed slopes and at lower elevations, several crusts likely exist in the upper snowpack which are generally well bonded.

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.