Avalanche Forecast

Issued: Mar 15th, 2016 4:30PM

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

ian jackson, Parks Canada

Banff Yoho Kootenay.

Heads up out there. The current snowpack is complex and Tuesdays avalanche control results show that large avalanches can be easily triggered with big triggers such as explosives and cornices.

Summary

Weather Forecast

A similar weather pattern for the next few days - on Wednesday expect overcast skies with light snow through the day, probably not accumulating more than 3-5cm. Temperatures will remain cool from -2 to -10 and relatively light winds. A gradual clearing trend into Friday. Excellent weather for quality tree skiing!

Snowpack Summary

The snowpack is complex right now. 30-70 cm of new snow sits on crusts below 1800m and on W through E aspects into the alpine. This has been reactive with explosives in many areas on Tuesday. On polar aspects, the new snow is bonding better, but the lower snowpack is still facetted and weak, with many avalanches stepping down to near the ground.

Avalanche Summary

A round of avalanche control on Mt Bosworth and Field in Yoho and Mt Whymper and the Simpson paths in Kootenay today produced numerous avalanches up to size 3. Many of these were running on sun crusts or melt freeze crusts and stepping down to the basal facets in thinner areas. Cornices were large and easy to trigger.

Confidence

Due to the number and quality of field observations

Problems

Deep Persistent Slabs

The mid-pack facets remain weak, especially in thin or rocky areas. Avoid steep or unsupported terrain, and watch for signs of instability such as whumpfing and cracking.

Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Persistent Slabs

Now that the sun is higher in the sky, buried suncrust becomes more of a problem. Presently there are several crusts buried on S through E aspects, with 30-70 cm overlying them. This problem is most significant in the south Kootenay region.

Dig down to find and test weak layers before committing to a line.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Wind Slabs

30-50 cms of new snow over the last few days sits on buried wind slabs from last weeks storm. Although these windslabs are becoming more stubborn, if triggered they could step down to the deeper weak layers.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

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