Avalanche Forecast

Issued: Apr 7th, 2016 9:22AM

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

jsmith, Avalanche Canada

Kootenay Boundary.

Freezing levels remain above the mountain tops. Failing cornices could trigger large avalanches running to valley bottoms. Watch out for what's above your head.

Summary

Confidence

High

Weather Forecast

FRIDAY: Freezing levels soar to 3500m, sunny, light southwest ridgetop winds that rise to strong Friday night out of the northwest. SATURDAY: Freezing levels remain around 3000m, sunny, light southwesterly ridgetop winds. SUNDAY: Freezing level 3000m, sunny, light southwesterly ridgetop winds.

Avalanche Summary

No new avalanches were reported in this region on Wednesday. However, I expect to see widespread natural loose wet avalanche activity on Thursday when the recent storm snow is heated by solar radiation and rapidly rising freezing levels.

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.Â 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.Â 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.

Problems

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.

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

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

3 - 6

Wet Slabs

Rapid warm ups can awaken dormant weak layers deep in the snowpack.

Avoid steep slopes with an isothermal snowpack during the heat of the day. >

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

3 - 6

Loose Wet

Changes can be rapid, sometimes significant change is possible in a matter of minutes, certainly within an hour or two.

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

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Apr 8th, 2016 2:00PM