Avalanche Forecast

Issued: Apr 7th, 2018 4:02PM

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.

Recent snowfall with strong winds has produced new slabs at higher elevations. Expect avalanche activity to increase on southerly aspects if the sun comes out.

Summary

Confidence

Moderate -

Weather Forecast

SUNDAY: A mix of sun and cloud, 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 rising to 2000 m by late afternoon.TUESDAY: Mostly cloudy with afternoon precipitation, accumulation 10 mm, alpine temperature 0 C, freezing level 2600 m dropping to 2000 m.

Avalanche Summary

On Friday, numerous storm and wind slabs were reported in the region.Â They were generally small to large (size 1 to 2), triggered by skiers, explosives, cornice falls, and naturally, and 5 to 20 cm thick.Â Many loose wet avalanches were also observed at all elevation bands.On Wednesday, skiers triggered a large persistent slab in alpine terrain. It was reported as a size 3, 50-200 cm deep.

Snowpack Summary

Around 30 cm of recent snow and strong southerly winds have created 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.Â On ridges, cornices are reported to be large and fragile. At lower elevations, precipitation fell 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. Expect thicker slabs in lee features due to strong southerly winds. Slab or loose wet avalanches could release naturally when the sun is out or the air temperature warms.

Observe for the bond of new snow with the old surface before committing into avalanche terrain.Use ridges or ribs to avoid pockets of wind-loaded snow.Avoid sun-exposed slopes when the solar radiation is strong, especially if snow is moist or wet.

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.

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

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.

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

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1.5 - 2.5

Valid until: Apr 8th, 2018 2:00PM