Avalanche Forecast

Issued: Feb 4th, 2015 4:00PM

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

grant statham, Parks Canada

Banff Yoho Kootenay.

The great conditions will continue until mid-day Thursday, but then it all changes. An avalanche cycle will be in full force by Friday with up to 40 cm expected, freezing levels to 2000m and winds exceeding 110 km/hr. Head for the trees!

Summary

Weather Forecast

The weather is changing as a strong system moves into the area embedded in a westerly flow. Expect 5-10 cm Thursday, 15-25 Friday, and 10 cm on Saturday. Significant warming and winds accompany this system, with freezing levels to 2000 m on Friday and SW wind exceeding 100 km/hr. This may not come true, as the models disagree on snowfall amounts.

Snowpack Summary

35-50 cm of recent storm snow sits on a crust from January 30, and in isolated locations (east of the divide) has been blown into windslabs. Over the next few days, as the next storm begins to add load, this bond to the Jan 30 interface will be critical. Expect windslabs by Thursday, with human triggered and natural avalanches likely by Friday.

Avalanche Summary

One natural size 2 avalanche was observed on Mt. Redoubt near Lake Louise, approximately 60 m wide and failing on the ground level depth hoar. Good backcountry observations were made from Sunshine Village and the Brewster Creek area, and no new avalanches were observed here.

Confidence

Intensity of incoming weather systems is uncertain on Friday

Problems

Wind Slabs

Windslabs exist in isolated areas at higher elevations, and this problem will increase late in the day on Thursday as the storm arrives. The bond to the surface under the windslabs is suspicious, so watch out as this new storm changes conditions.

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

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Deep Persistent Slabs

The base of the snowpack remains weak due to basal depth hoar/facets. Continue to avoid large open slopes with shallow snow and rocks, as this is the kind of place where this deep weakness could be triggered.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Feb 5th, 2015 4:00PM