Avalanche Forecast

Issued: Jan 8th, 2019 4:00PM

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

jonas hoke, Parks Canada

Jasper.

Large features without previous activity remain a concern, it is still possible to trigger very large avalanches.

Summary

Weather Forecast

The ridge of high pressure is replaced as a Pacific low moves inland today, with warmer air and snow flurries for Wednesday and Thursday.Wednesday: Cloudy with flurries (up to 6cm accumulation). Alp High -4C, Low -6C. Moderate SW ridge wind, freezing level 1600m.A detailed mountain weather forecast is available from Avalanche Canada.

Snowpack Summary

Moderate winds building fresh windslabs at ridgetop. Up to 85cm of snow fell between Jan 2-4. This overlies previous widespread wind effect from strong to extreme SW winds (many exposed areas were scoured to ground). The Dec. 11th layer persists mid-snowpack. The basal snowpack is weak in shallow areas - many recent avalanches failed on the ground.

Avalanche Summary

Continued reports to the south of human and explosive triggered large avalanches.Jan 5th helicopter control produced numerous large-very large avalanches. One very large avalanche on Sunset pk. buried the Parkway and destroyed 10-20 hectares of mature timber.A natural cycle of numerous large to very large avalanches occurred Jan 3rd and 4th.

Confidence

Problems

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.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 4

Wind Slabs

Moderate SW winds and warming temps continue to add to the windslab problem.

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

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2.5

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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1.5 - 3.5

Valid until: Jan 9th, 2019 4:00PM