Avalanche Forecast

Issued: Apr 20th, 2016 8:34AM

The alpine rating is below threshold, the treeline rating is below threshold, and the below treeline rating is below threshold. Known problems include Wet Slabs, Loose Wet and Cornices.

triley, Avalanche Canada

South Coast.

Spring Conditions. The ridge of HIGH pressure is breaking down, and a weak weather system is moving on-shore. Expect high freezing levels to continue to result in wet slab and loose wet avalanches.

Summary

Weather Forecast

High cloud developing overnight with light southerly winds and freezing levels down to 2000 metres. Light precipitation starting Thursday morning combined with light southwest winds and freezing levels rising up to 2500 metres. Cloudy on Friday with 3-5 cm of new snow above 2000 metres and light southwest winds. Continued overcast with light precipitation and light winds on Saturday.

Avalanche Summary

On Tuesday a size 3.0 wet slab avalanches was explosives triggered in the Duffey Lake area, this large avalanche released down to the ground on a northwest aspect at 2200 metres and ran to the valley bottom. Most commercial operations in the region have finished their season and data is sparse.

Snowpack Summary

Cornices are large, fragile, and could trigger deep slab avalanches that run to valley bottoms. Monitoring the overnight freeze of the snow surface is very important.. If the snow surface does not freeze overnight or if the crust is only a few cm thick, the effect of daytime heating and solar radiation will weaken the snowpack much quicker. There is an old crust layer down approximately 50cm in the Duffey area and north of Pemberton. Though mostly dormant, it produced a couple large avalanches during the last major warming event. The forecast hottest weather of the year to date could again test it, especially in isolated locations such as steep, rocky faces. Glide cracks are widespread, active, and best avoided. Low elevation and thin snowpack areas have become isothermal, meaning the snowpack is 0 degrees Celsius throughout. An isothermal snowpack is more prone to full depth wet slab avalanches during the heat of the day, especially on steep, smooth slopes.

Problems

Wet Slabs

Wet slab avalanches continue to be a concern due to strong solar radiation and high daytime freezing levels. Forecast cloud may decrease the likelihood once the freezing levels drop and new surface crusts form.

Avoid sun exposed slopes, especially where the snow is wet, weak, and mushy.>Avoid rocky, shallow or steep slopes during the heat of the day.>Travel early before the heat of the day, and avoid big slopes in the afternoon.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Loose Wet

Loose wet avalanches may continue due to one more day of high daytime freezing levels. If it rains before the surface re-freezes, loose wet avalanches will be very likely.

Start and finish early before the surface crusts melt.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Cornices

Cornices may continue to fall off naturally during periods of high freezing levels and warm daytime temperatures. Cornice falls may trigger wet slab avalanches.

Cornices become weak with daytime heating. >Pay attention to overhead hazards like cornices.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Apr 21st, 2016 2:00PM