Avalanche Forecast
Issued: Feb 8th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Deep Persistent Slabs and Persistent Slabs.
Tim Haggarty,
Parks Canada
With strong alpine winds in the forecast, expect significant wind transport over the next few days and increased potential for natural avalanche activity.
Summary
Weather Forecast
Strong W-NW alpine winds will develop Sunday morning. These are expected to diminish Monday before rebuilding Tuesday. Continued flurries for the period accumulating up to 10 cm of snow with alpine temps rising slowly from -15C values to -10C values.
Snowpack Summary
Up to 20cm in the past 48 hrs gives 40-80cm since January 31. Wind slabs exist in the alpine. A rain crust up to1900m is now buried by 15-30cm of snow. The Dec 31 layer of facets, surface hoar and sun crust is down 50-100cm. The deep persistent basal layer is ~30cm above the ground and is more developed in shallow snowpack areas.
Avalanche Summary
Skier triggered sz 2.5 in the Lipalian 3 in the Lake Louise backcountry Thursday, no injuries
Explosive work at local ski areas has seen the deep persistent layer fail, up to sz 2, to ground under light loads (1kg explosive = human load).
Last weekend's natural avalanche cycle saw large avalanches up to size 3.5 running to valley bottoms.
Confidence
Intensity of incoming weather systems is uncertain on Sunday
Problems
Wind Slabs
Wind over the last week has redistributed snow in the alpine creating wind effect and forming slabs. Strong alpine winds forecast for Sunday and Tuesday will develop these slabs and likely form them at treeline as well.
- If triggered the wind slabs may step down to deeper layers resulting in large avalanches.
- Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
High consequence deep releases on the facets and depth hoar at the base of the snowpack remain possible. Dealing with the uncertainty around this layer can be somewhat managed by avoiding large, committing terrain and areas with a thin snowpack.
- Avoid shallow snowpack areas where triggering is more likely.
- Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
This layer of surface hoar, facets and crusts is down 50 to 100cm and produces variable results, many in the hard range or no result.
- Dig down to find and test weak layers before committing to a line.
Aspects: All aspects.
Elevations: Treeline.
Likelihood
Expected Size
Valid until: Feb 9th, 2020 4:00PM
