Avalanche Forecast

Issued: Jan 11th, 2019 4:24PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is low. Known problems include Loose Wet and Storm Slabs.

dsaly, Avalanche Canada

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.

Summary

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

A major input of heat into the snowpack can stress deeper instabilities and activate buried weak layers. Use caution as the snowpack responds to the initial punch of rapid warming and spiking freezing levels.

Watch for clues, like sluffing off of cliffs, that the snowpack is warming up. Watch for terrain traps where small amounts of snow will acumulate into deep deposits.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Storm Slabs

Storm slabs have developed with recent snow and strong southerly winds. Deeper and more sensitive deposits of snow will be found in wind-loaded terrain: under cornices and roll-overs, cross-loaded areas, and lee terrain features.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Be alert to conditions that change with elevation.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Jan 12th, 2019 2:00PM