Avalanche Forecast

Issued: Apr 10th, 2018 4:14PM

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

swerner, Avalanche Canada

South Coast Inland.

Ridgetop winds are strong from the southwest, building reactive wind slabs at upper elevations. Rising freezing levels will weaken the snow surface and increase the likelihood of triggering avalanches.

Summary

Confidence

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

Weather Forecast

Wednesday: Mostly cloudy with scattered flurries. New snow 5-10 cm. Ridgetop wind strong from the southwest and freezing levels rising to 1800 m. Thursday: Mix of sun and cloud. New snow up to 5 cm. Ridgetop wind strong from the southwest and freezing levels 1200 m. Friday: Yet another blast of winter up high! Heavy snow. Up to 20 cm in the North and up to 40 cm in the South. Ridgetop winds strong-extreme from the southwest with freezing levels near 1500 m.

Avalanche Summary

On Monday, a small natural avalanche cycle was observed from southeast aspects around 2300m. Widespread whumphing was observed in a drainage in the north of the region, which was suspected to have been on the late-March weak layer described in the Snowpack Summary. 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 at treeline and above on leeward slopes. At lower elevations, loose wet avalanches may occur as the daytime temperature rises.

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

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

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

A weak layer buried 40 to 70 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.

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

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. Give them a large berth while on ridges and avoid traveling underneath them, as they may trigger avalanches on slopes below.

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

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Apr 11th, 2018 2:00PM