Avalanche Forecast

Issued: Jan 25th, 2018 4:00PM

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

stephen holeczi, Parks Canada

Banff Yoho Kootenay.

We have reached the tipping point for avalanches in most of the region, and a natural cycle occurred Thursday. We may see a decrease in natural activity for Friday, but slopes are primed for human triggering. Time to step way back.

Summary

Weather Forecast

A cooling trend for Friday with alpine highs of -16C, and valley bottom highs of -12C (-5C on the East slopes like Banff). Only 1-3cm of snow is expected with Westerly alpine winds in the 30-40kmh range.

Snowpack Summary

55-75cm of snow has fallen over the past 9-days creating a lot of loose snow on the surface. Alpine winds have distributed this into leeward areas with wind slabs up to 1m thick. Three persistent weak layers lurk in the upper half of the snowpack: Jan 16 down 20-40cm; Jan 6 down 30-50cm; Dec15 down 40-80cm giving easy-mod test results.

Avalanche Summary

We have hit the "tipping" point over the weak layers mentioned above and there is a natural avalanche cycle to size 3 occurring. Some avalanches are occurring in the new snow only, with some stepping down to the numerous weak layers below. Explosive control on Bosworth produced results to size 2 within the new snow.

Confidence

Problems

Persistent Slabs

There are 3 weak layers in the upper snowpack: Jan 16, Jan 6, and Dec. 15. All are a mix of sun crust, surface hoar and facets depending on your aspect and elevation. Avalanches are occurring on these layers

Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.Use conservative route selection, choose supported terrain with low consequence.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 3

Wind Slabs

With up to 75cm of snow over the past 9-days there is plenty of wind slab development available to be blown into touchy windslabs which should be anticipated in alpine and treeline areas.

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

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Jan 26th, 2018 4:00PM