Avalanche Forecast

Issued: Apr 13th, 2016 9:48AM

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

jsmith, Avalanche Canada

South Coast.

Spring conditions with a brief return to winter in the alpine. Expect to find touchy wind slabs sitting on slippery crusts.

Summary

Weather Forecast

THURSDAY: Freezing level: 1900m, mix of sun and cloud, light variable ridgetop winds. FRIDAY: Freezing level: 1700m, mostly sunny,Â light southerly ridgetop winds. SATURDAY: Freezing level: 2500m, mix of sun and cloud, light southerly ridgetop winds.

Avalanche Summary

No new avalanches were reported in this region on Tuesday. However, with the recent snow and wind I would expect to find thin wind slabs ripe for human triggers on lee features in the alpine on Thursday.

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 during the spring. 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. There is an old crust layer down approximately 50cm in the Duffey area and north of Pemberton. This layer has generally been dormant but resulted in a couple large avalanches during the last major warming event and produced a couple explosive triggered avalanches on Thursday. With continued warming, this layer could wake-up 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, rocky faces.

Problems

Wind Slabs

Be on the lookout for fresh thin wind slabs sitting on slippery crusts in the alpine.

Travel on ridgetops to avoid wind slabs on slopes below.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Cornices

If the sun is shining, cornices present a significant hazard. Even if they don't trigger a slab avalanche when they fall onto a slope, they have a nasty habit of running surprisingly long distances.

Cornices become weak with daytime heating, so travel early on exposed slopes. >Pay attention to overhead hazards like cornices.>Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 5

Loose Wet

Solar radiation in the spring can rapidly change the hazard from low to high. Plan ahead and monitor the effect of solar radiation carefully.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet. >Look for signs of surface instabilities such as pinwheeling and point releasing near cliffs. >

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Apr 14th, 2016 2:00PM