Avalanche Forecast

Issued: Apr 14th, 2017 8:02AM

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.

chris gooliaff, Parks Canada

Glacier.

Blustery winds and convective storms keep building wind slabs in the alpine. With wintery snow up high and Spring crusts down in the valley, the snowpack and conditions are quite variable.

Summary

Weather Forecast

Mixed weather for Friday, with sun and cloud, isolated flurries, freezing levels rising to 1400m, and moderate west winds. Tonight and into Saturday we should see another 10cm of snow with moderate to strong SW winds. Freezing levels will remain below 1500m.

Snowpack Summary

New snow from convective flurries overlies a series of crusts on most aspects up to 1900m. Reports of strong to extreme winds in the high alpine will have formed surface wind slabs. Cold, dry snow can be found on northerly slopes while solar aspects rapidly become moist with sunshine. Huge cornices line the upper ridges.

Avalanche Summary

Numerous natural avalanches to size 2.5 were observed in the highway corridor yesterday. All were failing within the recent storm snow and had shallow deposits. Neighbours surrounding Rogers Pass are still observing large natural avalanches, often triggered by large cornices.

Confidence

Due to the number of field observations

Problems

Wind Slabs

Winds have switched around to the SW and are building and redistributing surface wind slabs in alpine and tree-line lee features. These slabs may be quite sensitive to trigger if they sit upon a firm sun or temperature crust.

Avoid lee and cross-loaded terrain near ridge crests.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

There are multiple crusts in the upper metre of the snowpack, each providing a smooth sliding layer if avalanches dig down and trigger the deeper layers. Solar aspects are the biggest concern with day-time warming and a powerful April sun.

Choose well supported terrain without convexities.Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Cornices

The cornices are as big as they are going to get. Predicting their failure is tricky, but warming, heavy intense loading, or direct sun will weaken them. They have triggered some very large natural avalanches in and near Rogers Pass recently.

Stay well to the windward side of corniced ridges.Minimize exposure to overhead hazard from cornices.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Apr 15th, 2017 8:00AM