Avalanche Forecast

Issued: Apr 9th, 2017 4:50PM

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

cgarritty, Avalanche Canada

Cariboos.

The new snow is on a steady stabilizing trend, but avalanche hazards will persist the longest in wind affected areas. Watch for solar exposure to rapidly undermine stability.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Monday: A mix of sun and cloud. Light south winds. Freezing level to 1700 metres with alpine temperatures of -4.Tuesday: Mainly cloudy with scattered flurries and a trace to 5 cm of new snow. Light variable winds. Freezing level to 1700 metres with alpine temperatures of -4.Wednesday: Cloudy with sunny periods. Light to moderate east winds. Freezing level to 1900 metres with alpine temperatures of - 2.

Avalanche Summary

One 12-48 hour old Size 2.5 wind slab avalanche was reported on Friday. It occurred naturally on a steep, unsupported, north facing feature in the alpine.Several natural cornice falls up to size 3.5 were reported on Tuesday.

Snowpack Summary

Recent moderate to strong winds redistributed new snow from the past few days into wind slabs on a range of aspects in the alpine and at treeline. These wind slabs have developed above a mix of old surfaces that include melt-freeze crusts below about 1900 metres and on solar aspects in the alpine. Fragile new cornice growth also developed along ridgelines over the course of the week. Below the new snow, a number of storm snow and crust layers that formed over mid to late March appear to be well bonded. The February weak layers are now 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 produced large avalanches with cornice falls and other heavy triggers in late March and early April. They remain a concern and may be more likely to fail on southerly aspects during periods of strong solar radiation.

Problems

Wind Slabs

Recent moderate to strong wind shifted through a variety of directions, redistributing recent snowfall into wind slabs that now exist on a wide range of aspects. These slabs may remain reactive to human triggering, especially if exposed to the sun.

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 were responsible for triggering a number of large persistent slab avalanches last week.

Avoid 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

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 10th, 2017 2:00PM