Avalanche Forecast

Issued: Apr 8th, 2017 4:18PM

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.

Avalanche Canada cgarritty, Avalanche Canada

  The upper snowpack will gain strength overnight, but watch for breaks in cloud cover to undermine slab and cornice stability on Sunday. Spring sunshine packs a punch.

Summary

Confidence

High -

Weather Forecast

Sunday: Mainly cloudy with isolated flurries and a trace of new snow. Light southwest winds. Freezing level to 1800 metres with alpine temperatures of -3Monday: A mix of sun and cloud with flurries beginning in the afternoon. Light southwest winds. Freezing level to 1700 metres with alpine temperatures of -4.Tuesday: A mix of sun and cloud. Light northwest winds. Freezing level to 1700 metres with alpine temperatures of -5.

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 have been redistributing new snow from the past few days into wind slabs on a range of aspects in the alpine and at treeline. These new 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. 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

An icon showing Wind Slabs
Recent moderate to strong winds have shifted through a variety of directions, redistributing our new snow into wind slabs that now exist on a wide range of aspects. These slabs may remain reactive to human triggering on Sunday.
Keep an eye out for reverse loading created by shifting winds.Be especially careful with wind loaded pockets near ridge crests and roll-overs.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

An icon showing 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.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Persistent Slabs

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

3 - 4

Valid until: Apr 9th, 2017 2:00PM

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