Avalanche Forecast

Issued: Jan 27th, 2020 4:12PM

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

Parks Canada tim haggarty, Parks Canada

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With significant winds transporting snow to form wind slabs in the alpine, the likelihood of triggering serious slabs on the persistent and deep persistent layers is on the rise.

Summary

Weather Forecast

Light snowfall is expected Tuesday however amounts will favor the West side of the divide. Watch for winds to peak at strong in the alpine. Snowfall for Wednesday will be lighter however watch for alpine winds to reach extreme. By the end of the day Thursday, a significant system is expected to reach the forecast region.

Snowpack Summary

Recent wind slabs can be found near ridge-tops. There is 40-80 cm above the Dec 31 layer of facets, surface hoar and sun crust which produces variable test results through the region. The bottom layer of the snow-pack consists of weak facets and depth hoar, except for in deeper snow-pack areas (over 2m) where the basal facets are not as prominent.

Avalanche Summary

A large natural avalanche over Cascade waterfall occurred Friday failing on the basal facets/depth hoar . A size 2.5 Na was observed today on the S side on Mt Lipalian that looks 40-60 deep likely indicating a failure on the Dec 31 persistent layer. The forecasting trip to Takakkaw falls area saw few small wind slabs in the alpine.

Confidence

Intensity of incoming weather systems is uncertain on Tuesday

Problems

Persistent Slabs

An icon showing Persistent Slabs

The late December layer of surface hoar, facets or sun crust is buried 40-80cm throughout the region and produces variable results depending on location and what crystal form is present. Be suspicious on steep solar aspects and look for surface hoar.

  • If triggered the persistent slab may step down to deeper layers resulting in large avalanches.
  • Dig down to find and test weak layers before committing to a piece of terrain.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible

Expected Size

1 - 2.5

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

Generally the snowpack in the Little Yoho region is deeper and these layers are not as distinct. There area however areas, such as the ice climbs on Mounts Dennis and Stephen, that will display a shallower snowpack which must be treated with caution.

  • Avoid shallow snowpack areas where triggering is more likely.
  • Pay attention to overhead hazards like cornices which could trigger the deep persistent slab.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3.5

Wind Slabs

An icon showing Wind Slabs

Fresh wind slabs will continue to develop over the next several days with incoming snow and moderate to extreme winds expected in the alpine.

  • Use caution in lee areas. Recent wind loading has created wind slabs.
  • If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Jan 28th, 2020 4:00PM