Avalanche Forecast

Issued: Jan 25th, 2019 4:42PM

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

tim haggarty, Parks Canada

Banff Yoho Kootenay.

The windslab problem is likely to develop further with strong to extreme alpine winds in the forecast. With rising temperatures to consider as well, the potential for natural avalanche activity will increase through midday Sunday.

Summary

Weather Forecast

A warming trend started today and will continue through Saturday with freezing levels approaching 2000m, NW alpine winds increasing to Strong midday and the potential for light precip. Cooling will start Sunday as alpine winds shift to W and peak in the extreme range early in the day before backing off as the precip ends midday.

Snowpack Summary

10-20cm of snow over the last week over isolated suncrusts and surface hoar. Thin wind slabs can be found in alpine lee areas from strong SW winds on Saturday. Of greatest concern are the weak facets and depth hoar at the base of the snowpack. In thinner snowpack areas with less than 150 cm of snow, triggering a slab on these facets is more likely.

Avalanche Summary

Small windslabs failing off of the crest of the morraines above the iceline trail were seen on a field trip in the Little Yoho region today. The snow safety team at Sunshine Village reported fresh windslabs that had slowly formed over the last few days that were reactive to their ski cuts, one of which propagated 30m .

Confidence

Wind speed and direction is uncertain on Saturday

Problems

Deep Persistent Slabs

The weak Oct.26 facets and depth hoar at the base of the snowpack have a significant slab (50-130cm thick) sitting above them. The likelihood of triggering this layer has decreased, but if it does get triggered, the avalanche will be large in size.

Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.Avoid thin, rocky or unsupported slopes.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Wind Slabs

Thin wind slabs are currently stubborn and a bit old. Some are thinly buried near treeline but slabs still show potential for triggering and are more common in the alpine. These will build and may become touchy over the next two days.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Jan 26th, 2019 4:00PM