Avalanche Forecast

Issued: Apr 4th, 2018 3:40PM

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

pgoddard, Avalanche Canada

Sea To Sky.

Winter continues. Snow forecast for Thursday is expected to build new storm slabs.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

THURSDAY: 15-30 cm snow. Moderate to strong southerly winds. Freezing level near 1500 m.FRIDAY: Light snow. Light southerly winds. Freezing level near 1500 m.SATURDAY: Light to moderate snow. Light winds. Freezing level rising to 1750 m.Weather models disagree on the amount of snow expected this week.

Avalanche Summary

A handful of skier-triggered size 1 storm slabs were reported on Tuesday. The size and likelihood of storm slabs are expected to increase with Thursday's storm. Cornice fall remains a possibility. A cornice could tickle a deeply buried weak layer and trigger a surprisingly large avalanche.

Snowpack Summary

Forecast snow is expected to build new storm/wind slabs on Thursday. Cornices are reported to be large and fragile. New snow will overlie various old surfaces including existing storm slabs, melt freeze crusts on sunny aspects, scoured old hard wind slabs and dry snow.A weak layer consisting of surface hoar, facets or a sun crust buried in late March is now down about 60-80 cm. This is patchy in its distribution, but is mostly likely to be problematic on shady aspects between 1900m and 2250m. The mid and lower snowpack are strong and well settled.

Problems

Storm Slabs

Snow and wind are expected to build touchy slabs which could be triggered with the weight of a person. Cornices are also fragile.

Use conservative route selection: choose moderate angled and supported terrain with low consequence.Travel on ridgetops to avoid wind slabs on slopes below.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

Persistent slabs are most likely to be triggered with a large load like cornice fall; or by a person in a thin or variable-depth snowpack spot.

Avoid steep convexities or areas with a thin or variable snowpack.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

1 - 3

Valid until: Apr 5th, 2018 2:00PM