Avalanche Forecast

Issued: Jan 5th, 2015 4:48PM

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

tim haggarty, Parks Canada

Waterton Lakes.

A good time to be conservative as a storm threatens to tip the balance on the persistent weak layer. After the storm, watch for a temperature inversion Wednesday that may keep hazard elevated especially if combined with strong winds.

Summary

Weather Forecast

15cm, rising temperatures, and gusty alpine winds are expected with the passage of a warm front tonight. Tuesday morning as the cold front passes, expect winds to peak, temperatures to drop, and the precip to trail off. Watch out Wednesday for a strong inversion with freezing levels reaching 3000m and some potential for Strong West winds.

Snowpack Summary

160 to 200cm now at treeline. 30cm of snow accumulated since Friday now forms a very soft storm slab above faceted and wind affected surfaces. Cold temperatures slowed settlement in the 50 to 90 cm slab above the Dec 13 Crust/Facet and Dec 16 Surface Hoar layers. This has also promoted facet development above the crust and weakened this layer.

Avalanche Summary

Monday I triggered a south facing 40 degree slope at treeline by taking off my skis to dig a profile at the top of the start zone. Thankfully, only a 10cm crack formed at the crown in front of my feet, however cracks could be seen up to 50m away down the slope. Subsequent tests produced easy sudden planar shears on facets above the Dec 13 Crust.

Confidence

Freezing levels are uncertain on Wednesday

Problems

Persistent Slabs

Facets and isolated surface hoar above the Dec 13 crust remain the feature to watch in the snowpack. New load from storms or wind transport will make this more sensitive to triggering especially when combined with warm temperatures Wednesday.

Dig down to find and test weak layers before committing to a line.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Storm Slabs

The snow from the turbulent storm is forming a 30 to 40 cm soft slab at all elevations that fails very easily in tests over the cold low density snow from the weekend. Expect more development of these slabs at higher elevations with more wind effect.

If triggered the storm slabs may step down to deeper layers resulting in large avalanches.The new snow will requires several days to settle and stabilize.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Jan 8th, 2015 4:00PM