Avalanche Forecast

Issued: Mar 24th, 2017 4:28PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs, Persistent Slabs and Cornices.

cgarritty, Avalanche Canada

South Coast Inland.

Saturday will bring the end of the storm as well as a chance solar exposure. Wind slabs are already primed for human triggering, but a touch of sun may make them especially reactive.

Summary

Confidence

Moderate -

Weather Forecast

Friday night: Flurries bringing 5-10 cm of new snow. Strong southwest winds.Saturday: Mainly cloudy with continuing isolated flurries and a trace of new snow. Moderate southwest winds. Freezing level to 1300 metres with alpine temperatures around -5.Sunday: Mainly cloudy with isolated flurries and a trace of new snow. Light southeast winds. Freezing level to 1300 metres with alpine temperatures around -5.Monday: Cloudy with isolated flurries and a trace of new snow. Light to moderate southwest winds. Freezing level to 1700 metres with alpine temperatures around -1.

Avalanche Summary

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 20-30 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 that recently produced a few persistent slab avalanches and a crust/facet layer that appears 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. A chance of sun exposure may make these slabs especially reactive on Saturday.

Be increasingly cautious as you transition into wind affected terrain.Use ridges or ribs to avoid pockets of wind loaded snow.Minimize exposure to sun exposed slopes if the sun comes out.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Cornices

Recent warm and windy weather has been promoting cornice growth. While they are a hazard in themselves, the danger increases with wind slabs sitting beneath them. The chance of solar exposure may promote natural cornice falls on Saturday.

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

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Mar 25th, 2017 2:00PM