Avalanche Forecast

Issued: Feb 26th, 2017 4:00PM

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

Tim Haggarty, Parks Canada

Banff Yoho Kootenay.

The skiing is good however careful terrain selection remains critical right now to avoid triggering the deep persistent slab.

Summary

Weather Forecast

Cold nights overnight Sunday and Monday with a bit of cloud lingering with light winds. Watch for West winds to pick up on Tuesday with snow likely for the end of the day through Friday combined with a temperature increase.

Snowpack Summary

There is 15-25 cm of low density storm snow at tree line with a thin rain-crust below the storm snow at lower elevations. Some wind effect exists in the Alpine. Common throughout the region are the weak facets and depth hoar in the lower half of the snowpack, particularly at lower elevations and east of the divide.

Avalanche Summary

The ski hills have been working small windslabs isolated to the immediate lees of the last two days. Two size 2.5 natural avalanches were observed Friday on E-SE aspects in the alpine on Mount Ball and Mount Brett. Both appeared to scrub down to the ground.

Confidence

Due to the number of field observations

Problems

Deep Persistent Slabs

There is a thick slab over a structurally weak snowpack in most areas. Likely areas of triggering are in thin parts of a slope or rocky outcrops at tree line and above. A failure can propagate to deeper areas and cause large avalanches.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3

Wind Slabs

Gusty west winds on Saturday have created small wind slabs in the alpine with sluffing in steep gullies.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Feb 27th, 2017 4:00PM