Avalanche Forecast

Issued: Apr 15th, 2016 4:00PM

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, Deep Persistent Slabs and Cornices.

tim haggarty, Parks Canada

Banff Yoho Kootenay.

Watch for a weak freeze Saturday night to prime conditions for poor travel and likely an avalanche cycle Sunday and Monday as a ridge brings warm air and sunny skies.

Summary

Weather Forecast

Friday evening should see a reasonable freeze with a continued light ,slightly unstable, westerly flow. Freezing levels will reach 2500m Saturday afternoon but expect a weak freeze with warm air invading. Sunday watch for SIGNIFICANT HEATING: calm winds and clear skies allowing strong solar effect combined with freezing levels in excess of 3500m.

Snowpack Summary

5cm above a surface crust that stayed intact today above 1800m. Below the crust, isothermal snow exists up to treeline on all aspects, and in thin alpine areas on S aspects. N aspects in the high alpine are more winter like. In many places the upper snowpack sits on a weaker deep persistent layer of rounding facets.

Avalanche Summary

No new avalanches observed or reported today.

Confidence

Problems

Loose Wet

All avalanche terrain should be avoided later in the day when the crust on top of the snowpack breaks down due to daytime heating. This is possible to TL Saturday but very likely into the ALP and on North aspects Sunday with strong heating expected

Travel early on frozen crusts before the heat of the day.Watch for clues, like sluffing off of cliffs, that the snowpack is warming up.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Deep Persistent Slabs

Deep facet layers remain weak especially in thin snowpack areas and may be triggered during the hotter parts of the day. Sunday expect these slabs to become active especially on high North aspects that have yet to be heated to the forecast temps.

Travel early before the heat of the day, and avoid big slopes in the afternoon.If triggered the loose wet sluffs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Cornices

Watch for cornices to become active Sunday through Monday as the freezing levels reach their highest point yet this spring.

Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Apr 16th, 2016 4:00PM