Avalanche Forecast

Issued: Apr 13th, 2017 3:00PM

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.

triley, Avalanche Canada

Cariboos.

Winter continues at higher elevations, watch for wind slabs, reverse loading, and cornices that may be large and fragile.

Summary

Confidence

Moderate - Wind speed and direction is uncertain on Friday

Weather Forecast

Overnight: 3-5 cm of new snow with moderate southwest winds and freezing down to 800 metres. Friday: Overcast with a couple of cm of snow combined with moderate northwest winds and daytime freezing up to 1600 metres. Saturday: Overcast with flurries and moderate northwest winds and daytime freezing up to 1200 metres. Sunday: Mostly sunny with light winds and daytime freezing up to 1800 metres.

Avalanche Summary

Several natural cornice releases were reported up to size 2.5 on Tuesday. Explosive control produced cornice falls up to size 2.0 on Monday. Natural cornice falls up to size 2.5 were reported on Sunday from North aspects in the alpine between 2300-2400 metres.

Snowpack Summary

New snow and east winds have developed new wind slabs in the alpine and at treeline. These wind slabs are expected to continue to develop, and may result in reverse loading when the winds change and become westerly. Below the new snow, expect to find a series of crusts on solar aspects due to the recent diurnal melt-freeze cycle before the most recent storm. Cornices are reported to be large and fragile and continue to fall off naturally on a regular basis. 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

The wind during the storm has been from the east, and now the wind is forecast to change and come out of the west. This may create reverse loading, and wind loading on several aspects.

Use ridges or ribs to avoid pockets of wind loaded snow.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, South.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Persistent Slabs

A cornice fall or smaller slab avalanche 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 when the sun is out and solar radiation is strong.

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 14th, 2017 2:00PM