Avalanche Forecast

Issued: Apr 7th, 2017 4:37PM

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

Watch for variable wind loading patterns as you gain elevation and maintain avoidance 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 southwest winds. Freezing level to 1800 metres with alpine temperatures around -3.Sunday: Cloudy with sunny periods and isolated flurries with a trace of new snow. Light west winds. Freezing level to 1700 metres with alpine temperatures of -3.Monday: Cloudy with sunny periods. Light south winds. Freezing level to 1700 metres with alpine temperatures of -3.

Avalanche Summary

Reports from Thursday showed loose wet avalanches releasing both naturally and with skier traffic in steep terrain from Size 1-2. Isolated natural Size 1-2 wind slab releases were observed occurring in steep, rocky terrain as a direct result of wind loading.On Tuesday there was a natural cornice fall near Golden that did not release a slab on the slope below. On Monday there were several natural cornice falls up to size 2.5 that released storm or persistent slabs from the northerly aspect slopes below. On Sunday there was a natural cornice fall size 2.5 from extreme terrain.

Snowpack Summary

Light new snow amounts and moderate winds (mainly from the south) have formed fresh wind slabs on the snow surface at higher elevations. The new snow has buried melt-freeze crusts on all aspects below about 2200 metres and in the high alpine on solar aspects. Isolated surface hoar may be found below the new snow on shaded aspects at high elevations. Below the new snow interface, last week's storms brought 40-60 cm of snow to the region. Several other crusts as well as moist snow are likely to exist within this storm snow, mainly at lower elevations and on solar aspects. Fragile new cornice growth also occurred along ridgelines over the course of the week. At higher elevations, the February crust/facet layer is now down around 130-150 cm and the deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack. These layers were active during a storm in mid-March and produced some very large avalanches. Occasional deep releases were also reported in late March and these deeply buried weaknesses remain a serious concern as warming temperatures continue to penetrate the snowpack at increasingly higher elevations.

Problems

Wind Slabs

An icon showing Wind Slabs
Recent moderate to strong winds have shifted between a variety of directions and thin new wind slabs may now exist on a wide range of aspects. Slabs may be more reactive where they lie above recently formed crusts or more isolated surface hoar.
Keep an eye out for reverse loading created by shifting winds.Be especially careful with wind loaded pockets near ridge crests and roll-overs.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Cornices

An icon showing Cornices
Cornices have grown large and may break off naturally due to solar exposure or daytime warming. Cornice falls in motion have the potential to release persistent slabs on underlying slopes, resulting in large avalanches.
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.

Likelihood

Possible - Likely

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 and result in large avalanches.Recognize and avoid runout zones.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 4

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

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