Avalanche Forecast

Issued: Feb 6th, 2015 5:22PM

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

patrick jerome, Parks Canada

Banff Yoho Kootenay.

High freezing levels & precipitation with strong winds aloft are telltale signs that avalanche terrain is best avoided this weekend until the storm ends and temperatures cool things off. Avoid any avalanche terrain and make simple terrain choices. PJ

Summary

Weather Forecast

The Jet Stream is lined up in a north westerly flow on the east side of the Divide coupled with strong SW flow from the southern Pacific providing a positive moisture feed until Saturday afternoon with light snow through Sunday. The winds aloft will remain strong until Saturday evening. A break in the weather is expected by Monday morning.

Snowpack Summary

45 - 70 cm of recent storm overlies a crust from January 30th. The recent heavy precipitation, wind and warmer temperatures have created storm slabs which will put an enormous amount of stress on the January 30th crust interface. The basal facets from Nov 6th could reemerge in step down events with this huge stress to the snowpack.

Avalanche Summary

One natural size 2.5 avalanche narrowly missed a number of snow-shoers today in Lake O'Hara out the Schaeffer Bowl area. Several large avalanches up to size 3 were observed on the Highway 93S. Poor weather and embedded fog limited the forecaster's observations today but there were undoubtedly many more avalanches occurring than were seen today.

Confidence

Forecast snowfall amounts are uncertain on Saturday

Problems

Storm Slabs

Storm slabs are the primary issue in the upper snowpack and failures will be occurring both within the colder low density and on the January 30th crust interface. This problem will be most prominent in the alpine and treeline bands on all aspects.

If triggered the storm slabs may step down to deeper layers resulting in large avalanches.Avoid freshly wind loaded features.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 3

Deep Persistent Slabs

The base of the snowpack remains weak due to basal depth hoar/facets. Additional snow load, or a storm slab failure may trigger large to very large avalanches in thin snowpack areas. There were additional avalanches triggered on these facets today.

Avoid lingering in runout zones.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 4

Valid until: Feb 7th, 2015 4:00PM