Avalanche Forecast

Issued: Jan 10th, 2015 4:00PM

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

deryl kelly, Parks Canada

Jasper.

Wide variability in the sensitivity of the storm slab over the Dec 20 layer through the forecast area, be cautious out there.

Summary

Weather Forecast

Expecting seasonally cold temps and broken skies over the day Sunday. If the sun comes out for extended periods be aware of the possibility of increasing hazard on solar slopes and especially from rocky shallow areas in the sun. So, if you find yourself on a nice steep sunny slope slapping on sunscreen and having lunch, might be best to move on!

Snowpack Summary

Overall, field teams are finding a weak snowpack. The Dec 20 facet/surface hoar layer is out there. It was proving to be very sensitive to fluctuations in temp and solar radiation and showed exceptional propagating properties for having only a weak soft storm slab over it.

Avalanche Summary

A natural avalanche cycle up to sz 3 on south to westerly (solar) aspects occurred over the week. A dramatic temperature inversion at around 2500ms (cold air low/warm above) was actively affecting the slopes.

Confidence

Due to the number of field observations

Problems

Storm Slabs

Recent storm snow has settled into a soft slab which overlies a weak layer of facets and surface hoar. Temperature fluctuations and direct solar radiation may lead to an increased likelihood of avalanches.

Watch for whumpfing, hollow sounds, and shooting cracks.Be careful with wind loaded pockets while approaching and climbing ice routes.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Deep Persistent Slabs

This weak layer exists below a variable mid-pack at treeline and sub-alpine elevations. Large loads such as a cornice collapse or surface slides could still possibly trigger this deep persistent weakness.

Carefully evaluate and use caution around thin snowpack areas.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Valid until: Jan 11th, 2015 4:00PM