Avalanche Forecast

Issued: Mar 31st, 2016 4:00PM

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

stephen holeczi, Parks Canada

Banff Yoho Kootenay.

Avalanche control on Mts. Bourgeau, Whymper, Bosworth, Stephen and Wardle Friday. No outdoor activities there. Forecast clearing skies means high solar impact. Expect large avalanches in the region.

Summary

Weather Forecast

Friday looks like a crux day with freezing levels to 2500-2600m, light winds and a good chance this cloud will clear off giving a high solar input. Saturday will see increased cloud and a switch to a westerly flow with moderate W winds in the alpine and freezing levels up to 2500m.

Snowpack Summary

The snowpack is in transition between winter and spring, and is a poor example of both. There was a 2-4cm crust (thinner BTL) on solar aspects to ridgetop with moist snow underneath Thursday AM, and this crust is breaking down during the day. In many places the snowpack is sitting on a deep persistent layer of weak facets near the ground.

Avalanche Summary

A flight from the Wapta to Banff showed solar induced loose,wet avalanches to size 2 in the last 24 hours, and some deeper releases to size 2.5, mainly below steep cliffs in the alpine. Reports of many solar induced natural avalanches in Kootenay today to size 3.5 where the sun has been out all day. Many of these are stepping to ground.

Confidence

Timing or intensity of solar radiation is uncertain on Friday

Problems

Deep Persistent Slabs

Deep facet layers remain very weak, especially in thin or rocky areas. Avoid large open slopes, steep slopes (>30 degrees) and be wary that you can trigger this problem from a long distance away - the slab is stiff and it propagates far.

Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 4

Loose Wet

This problem is widespread, and expect slush style avalanches to be running in gullies, from cliffs and on steep slopes facing the sun.

If triggered the loose wet sluffs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 2

Cornices

Cornices are large. Give them a wide berth on ridge crests, as they can pull back a long way when they fail and may trigger avalanches below. If you need to travel under cornices, move quickly and think twice if there is significant heating.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3

Valid until: Apr 1st, 2016 4:00PM