Avalanche Forecast

Issued: Apr 10th, 2018 4:33PM

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.

swerner, Avalanche Canada

Sea To Sky.

New snow and forecast strong southwest winds will continue to build reactive storm slabs. Moist and wet surface snow will weaken with warmer temperatures and rain at lower elevations.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Up to 10 cm expected overnight on Tuesday. New snow 5-10 cm on Wednesday. Ridgetop wind strong from the southwest and freezing levels rising to 1500 m. Thursday: Mix of sun and cloud. New snow up to 5 cm. Ridgetop wind strong from the southwest and freezing levels 1300 m. Friday: Yet another blast of winter up high! Heavy snow, 30-40 cm expected. Ridgetop winds strong-extreme from the southwest with freezing levels near 1400 m.

Avalanche Summary

Several, natural storm slabs up to size 2 and loose wet avalanche activity from steep solar aspects were observed on Monday. Cornice control also produced size 2's but not pulling slabs from the slopes below. Avalanche activity will be on the rise with the incoming storm. Its still winter out there!

Snowpack Summary

Warm temperatures and rain have moistened the snow surface on all aspects and at all elevations with new snow accumulations in the alpine up to 15 cm on Tuesday. Reactive storm slabs and wind slabs are building with continued snow and strong southwest winds. Ridgelines are heavily corniced and could act as a trigger on the slope below. A weak layer consisting of surface hoar, facets, and/or a melt-freeze crust from late March is now buried about 60 to 120 cm. This layer is spotty in its distribution but has recently produced large avalanches. It is mostly likely to be problematic on west, north, and east aspects between 1900 m and 2250 m.Below this, the snowpack is well-settled and strong.

Problems

Storm Slabs

Storm slabs and loose wet avalanches may be reactive with warm and rainy weather. New storm slabs will form once the rain switches to snow. Slabs will be thicker in lee features, as the snow will fall with strong southwest winds.

Use ridges or ribs to avoid pockets of wind-loaded snow.Avoid steep slopes when air temperatures are warm, it is raining, or the solar radiation is strong.Use caution, especially in lee areas in the alpine and treeline. Storm snow is forming touchy slabs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2.5

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

Unlikely - Possible

Expected Size

2 - 3.5

Valid until: Apr 11th, 2018 2:00PM