Avalanche Forecast

Issued: Feb 18th, 2014 4:45PM

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

ian jackson, Parks Canada

Banff Yoho Kootenay.

Avalanche control is planned for Mt. Bosworth, Stephen and Field in Yoho and Mt. Whymper in Kootenay. Please no outdoor activities in these areas on Wed. Feb 19th.

Summary

Weather Forecast

A cold front will bring 5-15cm Tuesday overnight with moderate SW winds switching to NW as the system passes. We'll see a mix of sun and cloud with light flurries Wed and Thurs with a clearing trend towards the end of the week. Temps will cool to -10/-15 with the passing of the front on Wed AM.

Snowpack Summary

30 -70 cm of storm snow is settling and being blown into a cohesive slab which is overlying the weak Feb. 10th interface. This interface is a mix of sun crust, facets and surface hoar and will likely persist for a while. Additionally, SW winds have created wind slabs in lee alpine terrain which trigger easily and step down to the Feb. 10th layer.

Avalanche Summary

Evidence of a small cycle was observed today to size 3 as the recent storm snow has started to become a more cohesive slab. Notable events were multiple skiier triggered and explosives controlled avalanches to size 2.5 at the Lake Louise Ski Area and a size 3 natural off Mt. Wapta that buried the Tak Falls road with 1-2m of debris.

Confidence

Due to the number and quality of field observations

Problems

Persistent Slabs

The storm snow is starting to settle into a cohesive slab. As the slab stiffens, the weak layer will get harder to trigger, but the consequences will be greater. The nature and distribution of the weak layer means it will be with us for a while.

Avoid unsupported slopes.Avoid open slopes with any steepness over 30 degrees.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Wind Slabs

Recent SW winds are creating touchy windslabs in lee ALP and TL terrain. If triggered, these windslabs will step down to the Feb. 10th layer.

Be cautious as you transition into wind affected terrain.Use caution in lee areas in the alpine and treeline. Recent storm snow has formed touchy slabs.

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Feb 19th, 2014 4:00PM