Avalanche Forecast

Issued: Apr 11th, 2018 4:37PM

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.

swerner, Avalanche Canada

South Coast Inland.

The calm before the storm!Watch for wind slabs in the immediate lee side of ridgelines. They may be reactive to human triggers.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Thursday: Cloudy with some sunny periods. New snow up to 5 cm and strong southwest winds at ridgetop. Freezing level 1300m.Friday: Stormy. New snow 15-25 cm through the day. Ridgetop winds strong from the South. Freezing levels 1400 m. Saturday: The storm continues, bringing another 15-20 cm. Ridgetop winds strong from the southwest. Freezing levels 1500 m. Less snow amounts expected in the Northern areas of the forecast region.

Avalanche Summary

On Monday, a MIN report from the Duffy Lake area showed a skier accidental size 2 storm slab from a north aspect at 2700 m. Please check out the report here. No new observations on Tuesday or Wednesday, however, alpine observations seemed limited due to the weather. Expect the avalanche hazard to rise through the forecast period with new snow and wind.

Snowpack Summary

Up to 10 cm of new snow overlies moist snow surfaces. At higher elevations, this overlies slabs formed from last weekends snow that fell with strong southwesterly winds. On ridges, cornices are reported to be large and fragile. At low elevations below treeline, recent rain has created moist or wet snow conditions.A weak layer consisting of surface hoar, facets, and/or a melt-freeze crust from late March is now buried about 50 to 100 cm. This layer is spotty in its distribution. It is mostly likely to be problematic on west, north, and east aspects between 1900 m and 2250 m.The mid and lower snowpack are well-settled and strong.

Problems

Wind Slabs

Reactive wind slabs likely exist in isolated areas at treeline and above on leeward slopes. At lower elevations, loose wet avalanches may occur as the daytime temperature rises.

Watch for signs of instability such as whumpfing, or cracking. Avoid steep slopes when air temperatures are warm, or the solar radiation is strong.Use ridges or ribs to avoid pockets of wind-loaded snow.

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

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

A weak layer buried 50 to 100 cm is still surprising people and producing large and destructive avalanches. Be particularly cautious around upper treeline and alpine terrain on shady aspects, where this layer is most likely to be a problem.

Be aware of the potential for wide propagation due to the presence of buried weak layers.Avoid steep terrain or areas with a thin or variable snowpack.Pay attention to overhead hazards like cornices, which could trigger persistent slabs.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Cornices

Cornices are very large and fragile, especially when the sun comes out. Give them a large berth while on ridges and avoid traveling underneath them, as they may trigger avalanches on slopes below.

Pay attention to overhead hazards like cornices, which could trigger persistent slabs.Stay well back from cornices.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Apr 12th, 2018 2:00PM