Avalanche Forecast

Issued: Jan 25th, 2019 4:48PM

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

tim haggarty, Parks Canada

Little Yoho.

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

Wind Slabs

Some thin wind slabs have been triggered in isolated areas over the last few days. These slabs are now a bit old and even a bit buried. Watch for windslabs to develop further with the winds and small amounts of precip forecast for Saturday and Sunday

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

Deep Persistent Slabs

In Little Yoho, areas with a thin snowpack are still a question for forecasters. It is suspected that the deeper facet layers will be more prevalent in these areas . Check locally for snowpack depths as thicker regions do not have the same problem.

Be aware of the potential for wide propagations which could result in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

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