Avalanche Forecast

Issued: Apr 15th, 2017 7:37AM

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

andrew jones, Parks Canada

Glacier.

Winter conditions persists in the alpine with 10cm of new snow. Several crusts are buried in the upper snowpack and may be triggered by recently formed reactive wind slabs. Expect variable (challenging) ski conditions below treeline.

Summary

Weather Forecast

A mix of sun and cloud accompanied by isolated convective flurries. Ridge winds will be west 25km/h gusting to 50km/h. Freezing levels stay below1400m, but the afternoon sun can have a profound effect on steep solar aspects at all elevations. Temperatures climb higher on Sunday moving us towards spring conditions with warm days and cool nights.

Snowpack Summary

10cm of new snow at treeline. Settling storm snow in the top 60cm overlies a series of crusts on most aspects up to 1900m. Strong to extreme winds in the high alpine have formed wind slabs on lee features. 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

Several large natural avalanches were observed in the highway corridor yesterday in the size 2.0-2.5 range. Two size 3.0-3.5 avalanches were observed on the north face of Mt MacDonald including a deep slab release that cleared trees and ran to the end of the run out zone.

Confidence

Problems

Wind Slabs

Winds have switched around to the SW and are redistributing snow and building 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.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

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.

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

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Apr 16th, 2017 8:00AM