Avalanche Forecast

Issued: Feb 13th, 2014 4:57PM

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

stephen holeczi, Parks Canada

Banff Yoho Kootenay.

Avalanche conditions are `touchy` and the overall hazard is on the rise. Expect this trend to continue through the weekend. SH

Summary

Weather Forecast

Light gusting strong Westerly winds and 5cm forecast for Friday. 5cm on Sat then up to 20 cm with strong winds for Sunday. We expect the hazard to slowly increase during the weekend. Temperatures will be mild.

Snowpack Summary

Treeline storm snow amounts are 50cm in Kootenay and Yoho,35cm in the Sunshine area, and 20cm in the Louise/Hwy 93N areas. Winds,warm temps causing slab development in exposed areas,which overlies a complex layer of facets, surface hoar and sun crust on solar aspects. Below this a generally well settled midpack overlying the basal depth hoar layer.

Avalanche Summary

Field trip to Kootenay saw numerous naturals at all elevations to size 2.5 occur within the last 24 hrs. Forecasters were able to ski cut size 2`s which were low density slabs along ridgetops on the Jan 30th surface hoar. These were running 100-300m and were on average 30-40cm deep. Smaller slides were observed in other areas with less storm snow.

Confidence

Due to the number and quality of field observations on Thursday

Problems

Persistent Slabs

Touchy slabs are building and stiffening over a combination of facets, surface hoar, and sun crust on solar aspects. As the stiffness of the slabs increases, so too will the distance they propagate.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Wind Slabs

Winds will be forming slabs in the lee of ridge crests and exposed areas. These will be likely lying over facets or hard surfaces.

Avoid areas with overhead hazard.Avoid freshly wind loaded features.

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

Elevations: Alpine.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Deep Persistent Slabs

The basal depth hoar has been gaining strength and is lying dormant. We are waiting to see if this layer ``wakes up`` in thin snowpack areas this weekend with the new snow load.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Valid until: Feb 14th, 2014 4:00PM