Avalanche Forecast

Issued: Apr 10th, 2017 4:16PM

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

North Columbia.

Winter marches on at higher elevations. Wind slabs and cornice falls are the most likely problems. Persistent layers continue to exist in the snowpack, and may become reactive during periods of strong sun or daytime heating.

Summary

Confidence

High -

Weather Forecast

Overnight: Overcast with flurries and light southwest winds. Freezing down to 700 metres. Tuesday: 3-5 cm of new snow with light southwest winds and daytime freezing up to 1400 metres. Wednesday: Moderate southeast winds combined with another 3-5 cm of new snow in the morning and a chance of sunny periods in the afternoon. Daytime freezing up to 1600 metres. Thursday: Overcast with light snow and light southwest winds. Daytime freezing up to 1500 metres.

Avalanche Summary

Natural cornice falls and a couple of natural wind slabs size 2.0 were reported on Sunday. Some sluffing continues to be reported from steep shaded alpine terrain.

Snowpack Summary

5-15 cm of new snow added to the 30-40 cm of recent snow from a series of storms over the end of last week. The recent snow buried a mix of old surfaces that include melt-freeze crusts at treeline and below and on solar aspects in the alpine. Fragile new cornice growth also occurred along ridgelines over the course of the week. Below the new snow interface, 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 170-220 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 an ongoing concern and may be more likely to fail on southerly aspects during periods of strong solar radiation.

Problems

Wind Slabs

Variable wind directions over the past few days have developed wind slabs on several aspects in the alpine and at treeline. Forecast new snow may hide recent pockets of wind slab.

Keep an eye out for reverse loading created by shifting winds.Use ridges or ribs to avoid pockets of wind loaded snow.

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.

Pay attention to overhead hazards like cornices which could easily trigger persistent slabs.Avoid travel on slopes that are exposed to cornices overhead.

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 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, slab avalanches or cornices may step down to deeper layers.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

3 - 4

Valid until: Apr 11th, 2017 2:00PM