Avalanche Forecast

Issued: Mar 25th, 2017 4:46PM

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.

cgarritty, Avalanche Canada

South Coast Inland.

Avalanche problems increase with elevation. You may not see wind slabs releasing naturally on Sunday, but they are much more likely to react to cornice fall or human trigger.

Summary

Confidence

Moderate -

Weather Forecast

Sunday: Cloudy with scattered flurries bringing a trace to 5 cm of new snow. Light to moderate southeast winds. Freezing level to 1400 metres with alpine temperatures around -4.Monday: Cloudy with sunny periods and isolated flurries with a trace of new snow. Light southwest winds. Freezing level to 1700 metres with alpine temperatures of -2.Tuesday: Cloudy with scattered flurries bringing about 5 cm of new snow. Moderate to strong southwest winds. Freezing level to 1700 metres with alpine temperatures around -1.

Avalanche Summary

Reports from Friday showed wind slabs releasing to Size 1 with ski cutting in steep lee and crossloaded features as well as loose moist sluffs triggering naturally to Size 1 out of steep terrain.Reports from Thursday showed both natural and skier triggered storm and wind slabs releasing from Size 1-2 in the north of the region. Wind slabs were noted releasing above the melt freeze crust that was buried on March 22. In northern parts of the region, the deeper February weak layers continue to present a low probability / high consequence avalanche danger scenario.

Snowpack Summary

Steady light snowfalls over the week have deposited 25-45 cm of heavily wind affected new snow at upper elevations. Periodic rises in freezing levels to 2000 metres or higher over the same time period have been setting up a series of crust layers (March 20, 22, 23) within the upper snowpack at lower elevations and on solar aspects. A more widespread thick rain crust (March 15) exists up to 2100m and is now buried approximately 45-70cm below the surface. In the north of the region, the February weak layers are 100-140 cm deep and include a buried surface hoar layer as well as a crust/facet layer that appear to be gaining strength. In the southern parts of the region, the mid and lower snowpack are generally well settled and strong.

Problems

Wind Slabs

Light new snow amounts combined with moderate to strong southeast to southwest winds have been building wind slabs in the lee of exposed terrain features.

Use ridges or ribs to avoid pockets of wind loaded snow.Be increasingly cautious as you transition into wind affected terrain.Be alert to conditions that change with elevation.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Cornices

Recent warm and windy weather has been promoting cornice growth. While they are a hazard in themselves, the danger increases with the potential for a cornice fall to trigger a wind slab sitting below it.

Cornices become weak with daytime heating or solar exposure.Even small cornice falls may trigger larger avalanches.Pay attention to overhead hazards like cornices.

Aspects: North, North East, East, South East, South.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

In northern parts of the region, heavy triggers such as a cornice fall or a wind slab avalanche could potentially step down to weak layers buried about 1 m deep.

Carefully evaluate and use caution around thin snowpack areas.If triggered, wind slabs may step down to deeper layers and result in very large avalanches.Pay attention to overhead hazards like cornices which could trigger persistent slabs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Mar 26th, 2017 2:00PM