Avalanche Forecast

Issued: Apr 18th, 2016 8:14AM

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

triley, Avalanche Canada

Sea To Sky.

Spring Conditions. Sunny skies and very high freezing levels will increase the avalanche danger. The surface crust holds the snowpack together and may break down rapidly if there is no re-freeze overnight.

Summary

Weather Forecast

Overnight freezing level at 3500 metres under clear skies with light southwest winds. Clear and sunny on Tuesday with light southwest winds and freezing levels at 3500 metres. Clear and sunny on Wednesday with light winds and freezing level at 3500 metres. Some uncertainty regarding when the ridge of high pressure will break down; at this time about 50-50 chance of sun or cloud on Thursday. Freezing levels will start to drop after the ridge breaks down and moves eastward.

Avalanche Summary

No new avalanches reported, but we have very few eyes and ears still in the mountains reporting. Most commercial operations in the region have finished their season and data is becoming sparse.

Snowpack Summary

Cornices remain a concern, in part because of the potential to trigger wet 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 more quickly than it would if there is a well frozen thick crust. This is because the crust must first melt before the sun can weaken the snowpack. With the warmest weather this year forecast, layers in the mid snowpack and near the ground have the potential to wake up and become active. While isolated and unlikely, avalanches would be very large. 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, rocky faces.

Problems

Loose Wet

Sunny skies and high freezing levels will weaken the surface snow on solar aspects. Shaded aspects in the alpine may warm up enough to release as loose wet avalanches.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Cornices

Strong solar radiation and high freezing levels will continue to test remaining cornices in the alpine. Watch your overhead hazard and avoid traveling beneath corniced ridges.

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

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 6

Wet Slabs

The likelihood of wet slab avalanches will increase over the next few days with forecast high freezing levels and strong solar radiation. Be especially careful at mid and lower elevations where the entire snowpack is sloppy and unsupportive.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 6

Valid until: Apr 19th, 2016 2:00PM