Avalanche Forecast

Issued: Apr 14th, 2016 10:04AM

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.

ghelgeson, Avalanche Canada

Sea To Sky.

Friday is probably the last reasonable day for a big objective for the foreseeable future, as a significant warm up is expected to begin Saturday. The odd wind slab in the alpine may still be sensitive to human triggering.

Summary

Weather Forecast

Temperatures are expected to be on the cooler side again Friday before the big wave of warmth crashes into the region Saturday morning. FRIDAY: Freezing level starting at 1100 m, topping out at 1500 m, light to moderate southwest wind, no significant precipitation expected. SATURDAY: Freezing level beginning around 1500 m, climbing to around 2500 m in the afternoon, no significant precipitation, light variable winds at and below treeline, moderate southwest wind at ridgetop. SUNDAY: Freezing level beginning near 2800 m, rising to around 3500 m by the afternoon, no significant precipitation, moderate southwest wind.

Avalanche Summary

On Wednesday small storm and wind slabs to size 1.5 were reported running on a variety of aspects. On Tuesday, explosive control work near Whistler produced several size 2 cornice triggered avalanches.

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. Deeply buried weak layers in the mid snowpack and near the ground still have the potential to wake up and become active with a rapid warm up. While unlikely, releases on these deeply buried weak layers would result in very large avalanches. 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

Stay alert Friday, a few lingering wind slabs may still be sensitive to human triggering in the alpine.

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

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

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.

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

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Apr 15th, 2016 2:00PM