Avalanche Forecast

Issued: Apr 6th, 2013 4:00PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Storm Slabs, Cornices and Loose Wet.

garth lemke, Parks Canada

Jasper.

Saturday or Sunday's potential 15cm precipitation amount, relatively warm temperatures, high relative humidity in combination with wind loading patterns may be enough to overload the slippery crust interface it rests upon. Assess for this condition.

Summary

Weather Forecast

5-15cm of local snow accumulation may occur Saturday evening into Sunday evening. Winds will be shifting Northerly and Easterly yet remaining light with stronger ridgetop gusts. Freezing level is to be 1000m Saturday evening rising to 1700m Sunday afternoon then cooling trend Monday. Warm daytime temperatures expected to return on Tuesday.

Snowpack Summary

A melt freeze crust below treeline provides stability above a generally wet unconsolidated snowpack. By mid to early afternoon, daytime heat has the potential to break the crust down increasing the danger. Heating also promotes cornice failures which could initiate a large slide. Above treeline the snowpack is supportive but less so where shallow.

Avalanche Summary

No patrol on Saturday. On Friday, several loose avalanches were observed from steep rock cliffs. Alpine and treeline locations were not visible. Steep, Southerly aspects below 1600m are mostly melted out.

Confidence

Forecast snowfall amounts are uncertain on Sunday

Problems

Storm Slabs

Overnight snow accumulations may provide enough of a load to initiate slides on the temperature crust. Incoming North winds may load South aspects where this crust is well formed. Assess bonding of the new snow before committing.

Avoid freshly wind loaded features.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Cornices

These heavy and unstable features can fall unexpectedly triggering deep large avalanches. Daytime heating can increase the potential for their failure.

Pay attention to overhead hazards like cornices.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Loose Wet

This seems less of a concern the next couple of days with cooler temperatures but still a potential problem at low elevations. Be attentive to the air temperature and the thickness of the melt freeze crust particularly as the day progresses.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Apr 7th, 2013 4:00PM