Avalanche Forecast

Issued: Jan 7th, 2019 4:20PM

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

Cool arctic air remains over the region Tuesday. This ridge of high pressure will be replaced on Wednesday by a Pacific low giving warmer temps, rising freezing levels and precipitation midweek.Tuesday: Mix of sun and cloud. Alpine Low -19C, High -12 C. Ridge wind light SW. A detailed mountain weather forecast is available from Avalanche Canada.

Snowpack Summary

Moderate SW winds building fresh windslabs at ridgetop. Up to 85cm 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 - several recent avalanches failed on/near the ground.

Avalanche Summary

Jan 5th helicopter control produced numerous large-very large avalanches. One significant result on Sunset pk. was a very large avalanche, which buried the Parkway and destroyed 10-20 hectares of mature timber.Good visibility on this flight revealed that a natural cycle of numerous large to very large avalanches had 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.

Avoid thin, rocky or unsupported slopes.Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 4

Wind Slabs

Moderate to strong SW winds building fresh windslabs.

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, West, North West.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2.5

Persistent Slabs

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

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

Possible

Expected Size

1.5 - 3.5

Valid until: Jan 8th, 2019 4:00PM