Avalanche Forecast

Issued: Jan 2nd, 2014 5:05PM

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

Lisa Paulson, Parks Canada

Banff Yoho Kootenay.

We will tip into High hazard with the passage of tonight's snowfall & wind event. The intensity should taper by mid-day. The degree the hazard rises will depend on the amount of snow & wind loading that occurs. Be mindful of local snow amounts. LP

Summary

Weather Forecast

There is some discrepancy in forecasted snow for next 24 hrs. Could see 10-20 cm throughout most of the region through tonight and tomorrow morning with moderate to strong west winds accompanying the initial part of the storm. The rise in hazard will correspond to how much snow we receive and wind loading.

Snowpack Summary

Last weeks storm snow has settled to 35-40 cm W of the divide and 10-20 cm on the East. Continued west winds have added to the slab condition in the alpine and at treeline. The treeline snowpack depth is roughly 1 metre deep. The midpack is supportive on skis but is consists mostly of weak facets with a persistent weak layer at the ground.

Avalanche Summary

Avalanches to size 2.5 over the past few days have been reported with mainly the same characteristics, which are wind slabs failing to ground on the basal weaknesses. In the last 24 hrs, a storm/wind size 2.5 slab on Micheal Pk in Little Yoho area, NE alpine planar slope, had a long propagation of at least 300 m. It slid on an old snow surface.

Confidence

Forecast snowfall amounts are uncertain on Friday

Problems

Deep Persistent Slabs

This is the main layer of concern. Full depth avalanches to ground have occurred daily over the past week. This layer will be stressed further by tonight's storm increasing it's sensitivity to natural and human triggering.

Be aware of thin areas that may propogate to deeper instabilites.Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

2 - 3

Wind Slabs

Watch for areas of wind loading or open slopes with wind effect. If a wind slab is triggered it may step down to deeper layers.

Avoid freshly wind loaded features.Be careful with wind loaded pockets while approaching and climbing ice routes.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 3

Storm Slabs

This is mainly a problem in the main ranges where the 40-50 cm of storm snow is not yet bonded to the old snow. Shooting cracks and whumphing was observed at treeline west of the Divide as skiers attempted to access more open terrain.

Choose well supported terrain without convexities.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Jan 3rd, 2014 4:00PM