Avalanche Forecast

Issued: Apr 6th, 2018 4:24PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Storm Slabs, Persistent Slabs and Cornices.

mconlan, Avalanche Canada

Sea To Sky.

Snow is forecasted for Saturday with associated strong winds. Be cautious of periods of rapid precipitation or wind loading, as avalanche activity may increase.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

SATURDAY: Cloudy with snowfall, accumulation 10 to 20 cm, strong southerly winds, alpine temperature -3 C, freezing level 1600 m.SUNDAY: Mostly cloudy with light snowfall, accumulation 2 to 5 cm, light westerly winds, alpine temperature -3 C, freezing level 1600 m.MONDAY: Mostly cloudy, light southwesterly winds, alpine temperature -3 C, freezing level 1600 m.

Avalanche Summary

On Thursday, small loose dry, loose wet, and storm slab avalanches were reactive to skier triggers.On Wednesday, skiers triggered a large persistent slab in alpine terrain. It was reported as a size 3, 50-200 cm deep.

Snowpack Summary

New snow and strong southerly winds are creating new slabs at higher elevations. This snow overlies various old surfaces including previous storm snow, melt freeze crusts on sunny aspects, and old wind slabs. On ridges, cornices are reported to be large and fragile. At lower elevations, precipitation is falling as rain and creating wet snow conditions.A weak layer consisting of surface hoar, facets, or a sun crust from late March is now buried about 60 to 90 cm. This layer is spotty in its distribution but has recently produced large avalanches. It is mostly likely to be problematic on shady aspects between 1900 m and 2250 m.Below this, the snowpack is well-settled and strong.

Problems

Storm Slabs

Recent snowfall has formed new slabs. More snow is forecasted for Saturday, which will build thicker slabs. Observe for the bond of new snow with the old surface before committing into avalanche terrain.

Minimize exposure during periods of heavy loading from new snow, wind or rain.Use ridges or ribs to avoid pockets of wind-loaded snow.Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

A weak layer buried 60 to 90 cm is still surprising people and producing large and destructive avalanches. Be particularly cautious around upper treeline and alpine terrain on shady aspects, where this layer is most likely to be a problem.

Pay attention to overhead hazards like cornices, which could trigger persistent slabs.Be aware of the potential for wide propagation due to the presence of buried weak layers.Avoid steep terrain or areas with a thin or variable snowpack.

Aspects: North, North East, East, South East, South, South West.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Cornices

Cornices are very large and fragile. Give them a large berth if travelling on ridges and avoid travelling underneath them, as they can trigger large avalanches.

Give cornices a wide berth when travelling on ridges.Avoid travelling on slopes below cornices.

Aspects: North, North East, East, South East, South.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1.5 - 2.5

Valid until: Apr 7th, 2018 2:00PM