Avalanche Forecast

Issued: Apr 16th, 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 Sunday morning to prime conditions for poor travel and likely an avalanche cycle Sunday through Tuesday as a ridge brings warm air and sunny skies.

Summary

Weather Forecast

A weak freeze is expected Sunday morning as warm air invades from the south through the day. Watch for SIGNIFICANT HEATING as calm winds and clear skies allow strong solar effect combined with freezing levels in excess of 3500m. With no freeze expected Monday or Tuesday expect the heating effects to compound each day as freezing levels reach 3800m.

Snowpack Summary

5 to 10cm recent snow sits on a well established melt-freeze crust on all aspects. This surface snow became moist today with solar heating slopes. N aspects in the high alpine above 2600m remain more winter like having yet to receive a significant warm up. In many places the upper snowpack sits on a weaker deep persistent layer of rounding facets.

Avalanche Summary

Loose wet activity to sz 2 on steep solar slopes with the surface snow failing over the melt-freeze crusts.

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. Expect a poor freeze Sun am and NO FREEZE Mon and Tues.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 2

Deep Persistent Slabs

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

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3

Cornices

Watch for cornices to become active Sunday through Tuesday 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

Likely - Very Likely

Expected Size

1 - 2

Valid until: Apr 17th, 2016 4:00PM