Avalanche Forecast

Issued: Apr 23rd, 2014 4:00PM

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

Lisa Paulson, Parks Canada

Banff Yoho Kootenay.

Pay attention to how strong the overnight freeze is and how quickly it warms during the day. Start early and finish before it warms up. Cornice failures continue to occur, be mindful of overhead hazard.

Summary

Weather Forecast

Freezing levels to valley bottom tonight and some clear skies will help the overnight freeze. Cloudy skies forecasted tomorrow with mid mountain highs around -2 along the Divide. Periods of sun can be expected along the eastern part of the region.

Snowpack Summary

Cooler day today. Windslabs developing in the alpine 20-40 cm thick sitting on a crust. Freezing levels to valley bottom tonight with periods of clear skies. Moist snow in afternoon on solar aspects up to ridgetops and to 2400 m on polar aspects. Random patches of isothermal wallowing in thinner snowpack areas below treeline.

Avalanche Summary

No new avalanches observed in patrols today down to Field and up to Bow Summit. Monday was warmer with more sun and we saw a loose snow avalanche cycle up to Class 2 running out of steep rocky terrain through most of the region. Debris generally ran to top of runouts. No slab avalanches observed.

Confidence

Problems

Wind Slabs

Isolated windslabs 20-40 cm thick were found in the lees of features in the Bow Summit & Lake Louise region. They rest on an old temperature crust. Propagations up to 20 m observed.

Use caution in lee areas. Recent wind loading have created wind slabs.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Loose Wet

Loose wet avalanches are possible in the afternoon as a result of day time heating. Monitor how thick the crusts are and how quickly they break down during the day.

Avoid avalanche terrain during periods of rain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Deep Persistent Slabs

Although unlikely, it is still possible to trigger a slab avalanche on one of the deep persistent layers. Skier triggering of this layer is more likely in shallow snowpack areas.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Apr 24th, 2014 4:00PM