Avalanche Forecast

Issued: Apr 10th, 2015 9:15AM

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

bcorrigan, Avalanche Canada

Sea To Sky.

Incoming precipitation with strong winds will be the driver of the avalanche hazard for the next 3 or 4 days.

Summary

Confidence

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

Weather Forecast

A pacific frontal system will bring rain at the lower elevations and snow above 1000m for the next 3 days. This evening, (Friday) cloudy with snow flurries, 10 to 15cm of snow, light to moderate south west winds and freezing level hovering around 1000m. SATURDAY: Cloudy with flurries, 5 cm of snow expected, freezing level around 1000m, strong South winds. SUNDAY: 5 cm of snow, freezing level at 1000m, strong westerly winds. MONDAY, 10 to 15cm of snow, freezing level around 1200m, and winds moderate from the west.

Avalanche Summary

Snowballing and/or pin-wheeling on solar aspects was the last acivity reported during the warm clear spell of weather that just finished. Expect wind slab activity and cornice failures with the current weather pattern and increased loading.

Snowpack Summary

20 to 30cm of incoming precipitation will fall on a variety of crusts and old surfaces including surface hoar and facets in sheltered locations from the recent clear weather. Moderate to strong south west winds will redistribute the storm snow into wind slabs on the lee sides of ridge tops. A facet/crust layer buried in mid-March has been producing hard and sudden results in snowpack tests. This remains a concern in the region due to it's potential to produce very large avalanches. Cornices are also a concern these days. A cornice failure may trigger a large destructive avalanche.

Problems

Wind Slabs

Strong winds from the south west will redistribute the storm snow into wind slabs on exposed lee slopes. A big enough wind slab might trigger deeper instabilities

Avoid freshly wind loaded features.>Highmark or enter your line well below ridge crests to avoid wind loaded pillows.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Persistent Slabs

There are two persistent weak layers still present in the upper snowpack. These haven't been reactive for a few days now, but intense spring sun, a wind slab or cornice failure could be enough to reawaken this problem.

Avoid convexities or areas with a thin or variable snowpack.>Be aware of the potential for large, deep avalanches due to the presence of a buried crust/facet layer.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Cornices

Additional loading from the incoming storm may be enough to tip the scales on some large, ripe cornices and initial a failure. A large cornice dropping onto a slope might initiate a failure of a deeply buried weak layer.

Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 4

Valid until: Apr 11th, 2015 2:00PM