Avalanche Forecast

Issued: Nov 12th, 2018 4:00PM

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

ian jackson, Parks Canada

Banff Yoho Kootenay.

Good ski conditions exist if you are in high, smooth terrain, but the snowpack is thin. Watch for typical early season hazards and areas where the October 26th crust may be most reactive: shaded alpine lee areas.

Summary

Weather Forecast

The ridge of high pressure will remain for one more day with an inversion setting up. This means warmer temperatures in the alpine than in the valley bottom and the potential for valley cloud west of the divide. On Wed/Thurs, the ridge breaks down with up to 20 cm of snow by the end of day Thursday with strong westerly alpine winds.

Snowpack Summary

In the alpine, 20-50 cm of facetted and wind effected snow sits on the October 26th temperature crust. This crust is found in the alpine, mainly on shaded and lee aspects (where the October snow didn't completely melt) and has weak facets above and below. Total snowpack depths are 60-120 cm+ in the alpine, tapering quickly at treeline and below.

Avalanche Summary

Sunshine and Lake Louise ski hills reported isolated small windslabs still being triggered in steep, lee alpine terrain on Monday. On the deep persistent layer, natural and explosives triggered avalanche activity has tapered, but isolated whumphing still indicates triggering is possible.

Confidence

Timing, track, or intensity of incoming weather system is uncertain on Wednesday

Problems

Deep Persistent Slabs

The Oct 26th temperature crust is most reactive where it is buried far enough off the ground to create a smooth sliding surface. This is in shaded alpine lee terrain. Isolated whumphing is occurring on this layer, indicating it is still triggerable

If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.Whumpfing is direct evidence of a buried instability.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Wind Slabs

Isolated wind slabs exist in the lee of alpine features and have been reactive to explosives and ski cutting. Although small, these could be consequential if you are in steep terrain.

Use caution in lee areas. Recent wind loading has created wind slabs.Be careful with wind loaded pockets while approaching and climbing ice routes.

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 1.5

Valid until: Nov 13th, 2018 4:00PM