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Avalanche Forecast

Archived

Jan 11th, 2019–Jan 12th, 2019

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Sea To Sky.

Get ready for a warm weekend. A rapidly warming snowpack can quickly lose strength and stress buried instabilities. Best to choose conservative terrain and be aware that conditions may deteriorate through the day limiting your exit plans.

Confidence

Low - Freezing levels are uncertain

Weather Forecast

FRIDAY NIGHT: Mostly cloudy. Light south-southwest wind gusting strong. Alpine temps around +2C, freezing level rising above 2000m with a weak inversion.SATURDAY: Cloudy with sunny period. Moderate south wind gusting strong. Alpine temps reaching +4C, freezing level rising above 2000 m.SUNDAY: Mainly cloudy. Light south wind with occasional moderate gusts. Alpine temps reaching +6C, freezing level above 2100 m.MONDAY: Mix of sun and cloud. Light south-southeast wind. Alpine temps reaching +6C, strong alpine inversion.More details can be found in the Mountain Weather Forecast.

Avalanche Summary

On Thursday morning, a natural storm slab avalanche cycle size 2-3 was reported on rocky features around 2000 m and loose wet avalanches were reported below 1700 m. Explosives triggered numerous size 1-2 storm slabs with good propagation across features. A MIN report from Thursday in Area 51 noted a rapid temperature rise and skiers triggered storm slab avalanches. See the MIN here.Numerous storm slab avalanches to size 2 were triggered by explosives and skiers on Wednesday. Additionally, a large (size 2) cornice failed under the weight of a person. On Monday, Several small wind slabs were triggered by skiers near ridge crest.

Snowpack Summary

Recent rain and freezing levels rising to 1600 m has promoted rapid snowpack settlement at lower elevations. At higher elevations, recent snow has settled to 30-50 cm and has been redistributed by moderate to strong south winds. Cornices have grown and the storm snow has been reactive to skier traffic. As freezing levels reach the alpine, rapid warming in the snowpack can lead to loose wet avalanches.The new snow has buried old wind slabs on a variety of slopes at alpine and treeline elevations. At treeline and below, two weak layers exist in the upper 2 m of the snowpack. These layers consist of surface hoar (feathery crystals) in more sheltered areas and a crust on solar aspects and on all aspects below 1600m.In the lower snowpack, a crust/facet (sugar snow) layer is now over 2 m deep. There have been no recent reports of avalanches on this layer, but it may still be reactive to heavy loads (such as a cornice fall) in isolated areas.

Problems

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.

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.