Avalanche Forecast

Issued: Apr 15th, 2016 10:34AM

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.

ghelgeson, Avalanche Canada

Sea To Sky.

The heat is on! If you're hoping to get one more alpine mission in, you need to get out super early Saturday and plan to be out of avalanche terrain no later than lunch time. Watch for the odd small wind slab in the alpine Saturday morning.

Summary

Weather Forecast

A significant pattern change is expected to commence Saturday as a strong ridge begins to build. After Friday night, temperatures are expected to remain well above freezing at all elevations for the foreseeable future. SATURDAY: Broken cloud cover, freezing level beginning around 1200 m, climbing to around 2500 m in the afternoon, no significant precipitation, light variable wind at and below treeline, moderate southwest wind at ridgetop. SUNDAY: Few clouds, freezing level beginning near 2700 m, rising to around 3500 m by the afternoon, no significant precipitation, moderate southwest wind. MONDAY: Mostly clear skies, freezing level near 3500 m all day, no significant precipitation, light south/southeast wind.

Avalanche Summary

On Thursday a size 1 storm slab was accidentally triggered by a skier on a north aspect at 2300 m. The slab ran on the crust that's just underneath the most recent storm snow. 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

Loose Wet

Rising temperatures and periods of direct sunshine on Saturday will likely initiate a fresh round of loose wet activity as the storm snow from earlier this week looses cohesion.

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. >Start and finish early before the surface crusts melt.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

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 cornices and give them a wide berth when traveling on or below ridges. >Cornices become weak with daytime heating, so travel early on exposed slopes. >

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Wet Slabs

Rapidly warming temperatures and little to no overnight recovery this weekend will increase the potential for deep wet slab release.

Cornice releases have the potential to trigger deeply buried weak layers. Avoid rocky, shallow, and/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

Unlikely

Expected Size

4 - 7

Valid until: Apr 16th, 2016 2:00PM