Avalanche Forecast

Issued: Apr 7th, 2017 4:40PM

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

cgarritty, Avalanche Canada

Cariboos.

Watch for variable wind loading patterns as you gain elevation and maintain awareness of overhead hazards like cornices and large avalanche paths. A heavy trigger in the right location still risks triggering a very large and destructive avalanche.

Summary

Confidence

High -

Weather Forecast

Saturday: Mainly cloudy with isolated flurries and a trace of new snow. Light to moderate south winds. Freezing level to 1700 metres with alpine temperatures of -4.Sunday: Mainly cloudy with isolated flurries and a trace of new snow. Light south winds. Freezing level to 1700 metres with alpine temperatures of -4.Monday: A mix of sun and cloud. Light southeast winds. Freezing level to 1900 metres with alpine temperatures of -3.

Avalanche Summary

No new avalanches were reported on Wednesday or Thursday.On Tuesday several natural cornice falls up to size 3.5 were reported, and several natural cornice falls were reported on Monday up to size 3.0.

Snowpack Summary

Recent light snowfall combined with moderate winds (mainly from the southwest) to form new wind slabs in the alpine and at treeline. These new wind slabs have been developing above a mix of old surfaces that include melt-freeze crusts below about 1900 metres and on solar aspects in the alpine. In some areas the new snow may hide some lingering wind slabs that are left from the last stormy period. Cornices have been a primary avalanche problem in the past week, with recent reports of cornices breaking off naturally with loading from wind, or due to warming from direct sun or daytime heating. The February weak layers are down about 120-150 cm and the deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack. These deep weak layers have recently produced large avalanches with heavy triggers like cornice falls, and they may be more likely to fail on southerly aspects during periods of strong solar radiation.

Problems

Wind Slabs

Moderate to strong southwest winds recently shifted from southeast to northwest, redistributing our new snow into wind slabs that may now exist on a wide range of aspects. Expect these slabs to remain reactive to human triggering on Saturday.

Use ridges or ribs to avoid pockets of wind loaded snow.Be especially careful with wind loaded pockets near ridge crests and roll-overs.Keep an eye out for reverse loading created by shifting winds.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Cornices

Cornices have grown large and may fall off naturally with solar effect or daytime warming. Cornice falls have recently been responsible for triggering large persistent slab avalanches.

Do not travel on slopes that are exposed to cornices overhead.Pay attention to overhead hazards like cornices which could easily trigger persistent slabs.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3

Persistent Slabs

A cornice fall or smaller slab avalanche currently has the potential to trigger large, destructive avalanches on deeply buried weak layers. This is more likely to occur in thin or variable snowpack areas at higher elevations.

Recognize and avoid avalanche runout zones.If triggered, wind slabs or cornices may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

3 - 4

Valid until: Apr 8th, 2017 2:00PM