Avalanche Forecast

Issued: Jan 9th, 2019 4:00PM

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

timothy johnson, Parks Canada

Jasper.

Watch out for building wind slabs and cornices.

Summary

Weather Forecast

A "dirty" ridge of high pressure is bringing light precip to Jasper. A strong ridge then builds, bringing clear skies and warm temps for the rest of the week. Thursday: Cloudy with flurries (10cm). Alp High -5C, Low -6C. Moderate to strong W ridge wind, freezing level 1600m.A detailed mountain weather forecast is available from Avalanche Canada.

Snowpack Summary

Moderate to strong winds and 10cm of forecast snow will be building fresh wind slabs at ridge top. The snow from last week is settling into a cohesive layer overlying previous widespread wind effect, the Dec. 11th layer in the mid-snowpack and a weak facet layer on the ground in shallow areas - many recent avalanches failed on the ground.

Avalanche Summary

Continued reports to the south of natural triggered large avalanches.Jan 5th helicopter control produced numerous large-very large avalanches. One very large avalanche on Sunset peak buried the 93N and destroyed 14 hectares of mature timber.

Confidence

Intensity of incoming weather systems is uncertain on Thursday

Problems

Wind Slabs

Moderate - strong W winds and warming temps continue to add to the wind slab problem.

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: North, North East, East, South East, North West.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2.5

Deep Persistent Slabs

The base of the snowpack is weak and facetted in shallow areas and will likely be for some time. The new snow in combination with a skier has the potential to overload this weakness.

Avoid steep convexities or areas with a thin or variable snowpack.Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 4

Persistent Slabs

The Dec. 11th layer of facets and surface hoar is buried more than a meter deep. This layer is strengthening but was active during the recent storm.

Dig down to find and test weak layers before committing to a line.Be aware of the potential for wide propagations.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1.5 - 3.5

Valid until: Jan 10th, 2019 4:00PM