Avalanche Forecast

Issued: May 4th, 2017 8:22PM

The alpine rating is below threshold, the treeline rating is below threshold, and the below treeline rating is below threshold. Known problems include Wet Slabs, Deep Persistent Slabs and Cornices.

Lisa Paulson, Parks Canada

Banff Yoho Kootenay.

A widepread avalanche cycle continues where large avalanches are running well below treeline into snowfree bushy runouts. There is no overnight recovery. It's time to AVOID ALL AVALANCHE TERRAIN AND RUNOUTS. The hazard will remain HIGH to EXTREME.

Summary

Weather Forecast

Freezing levels remaining at 3600 m overnight, will cool only slightly on Friday remaining at 2800-3000 m through the weekend with showers and rain forecasted. Winds will be generally light from the SW.

Snowpack Summary

Moist surface snow and a variety of melt freeze crusts in the alpine. Unsupportive isothermal conditions exist at treeline and below. The basal weakness persists in the alpine and is reactive to large triggers and the current warm weather, 3600 m freezing level, & solar input.

Avalanche Summary

Today there were numerous large natural and explosive controlled size 3-4 wet avalanches. Avalanches are running far into below treeline terrain and may affect some hiking terrain. It's a good time to AVOID AVALANCHE TERRAIN completely and pull out the bike and rock gear!

Confidence

Problems

Wet Slabs

Large wet avalanches are occurring on all aspects and elevations and running far into the bushy snow free run outs.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Certain

Expected Size

1 - 4

Deep Persistent Slabs

There are numerous large avalanches running to ground at all elevations. This will continue for the next few days while freezing levels remain high.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Very Likely - Certain

Expected Size

3 - 4

Cornices

Cornices are big this time of year and will fall off at some point in the next few weeks. They will be more frequent with the forecasted warming and solar effect over the next few days.

Pay attention to overhead hazards like cornices which could trigger the deep persistent slab.Cornices become weak with daytime heating, so travel early on exposed slopes.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Very Likely - Certain

Expected Size

2 - 3

Valid until: May 5th, 2017 4:00PM