Avalanche Forecast

Issued: Mar 13th, 2019 4:12PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Wind Slabs and Loose Dry.

stephen holeczi, Parks Canada

Little Yoho.

The danger is Moderate, but will change fast with inputs like sun, wind, etc. This is due to the fact that we have prominent facets that are fickle to these inputs, and haven't had warmer spring temperatures yet. Watch for these changes locally.

Summary

Weather Forecast

Thursday will see temperatures near 0C at valley bottom and around -10C at 3000m. W winds will increase in the afternoon into the moderate range at 3000m with no new snow expected. There could be increased solar input especially in the E with less cloud cover. A big warmup is predicted next week which will be something to watch out for.

Snowpack Summary

15-30cm recent low density snow over previously wind blown surfaces in the alpine, and 30-50cm of facets below. In little Yoho the snowpack is generally thicker and settled, except for thin areas which have facets to ground. Steep areas continue to produce sluffing in many areas with buried suncrust on steep S aspects.

Avalanche Summary

Avalanche control today in Yoho confirms the combination of smaller (size 2) wind slabs entraining facets producing avalanches that run far for their mass. Slides to size 3 were produced on Mount Field and Bosworth where they entrained facets, and only produced smaller slides where they did not. Other areas out E have far less activity.

Confidence

Problems

Wind Slabs

New snow and strong SW winds have built slabs in open areas above treeline. These slabs are sitting on the weak, faceted snow that was previously on the surface and as a result can run further than expected when triggered.

Use caution in lee areas. Recent wind loading has created wind slabs.Watch for surface cracking and stiffer surface layers of snow.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Loose Dry

If triggered on their own, loose dry avalanches that are smaller in size can be initiated in steep terrain. If triggered by a wind slab, much larger avalanches that can run far are possible as they entrains facets on the way down.

Use caution above cliffs and terrain traps where small avalanches may have severe consequences.Be very cautious with gully features.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Mar 14th, 2019 4:00PM