Avalanche Forecast
Issued: Jan 18th, 2021 4:32PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
Marcus Waring,
Wind slab remains the primary concern in Waterton but last weeks storm was a reminder of the potential for large triggers to awaken weaknesses deep in the snowpack.
Summary
Weather Forecast
Tuesday- Cloudy with isolated flurries. Trace snow at Cameron Lake. Strong SW wind. Freezing level valley bottom.
Wednesday - Cloudy with Sunny periods. No precipitation. Moderate SW wind with strong gusts. Freezing level valley bottom.
Thursday- Mix of sun and cloud. Moderate, maybe even light, SW wind. Freezing level remaining at valley bottom.
Snowpack Summary
There is a surface melt freeze crust up to 1900m on all aspects. Recent storm was accompanied by strong to extreme Westerly wind creating stiff Wind Slabs in lee areas. Multiple layers of wind slab sit over the Dec 9th crust which can be found down 70-100cm near Cameron Lake. Areas east of the divide hold a thin & faceted snowpack.
Avalanche Summary
Public reports in the Wall Lake area mention increased wind slab reactivity in snow pack testing.
Last week we observed a widespread avalanche cycle from Size 1 to 3 that occurred on Tues PM / Wed AM. Some of these involved step down avalanches to deeper weak layers, including a size 3 with impressive propagation in a thin convexity in Rowe Bowl.
Confidence
Problems
Wind Slabs
Cooling temperatures have stiffened recently formed wind slabs. These stubborn wind slabs may be difficult to trigger, but the consequence would be large as stiff wind slabs will propagate far if initiated.
- Use caution in lee areas. Recent wind loading has created wind slabs.
- Choose low angle and supported terrain. Avoid large features.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Isolated persistent slab avalanches were observed after the last storm. This a reminder that they can still be triggered by cornice fall or smaller avalanches stepping down in thin snowpack areas.
- If triggered the wind slabs may step down to deeper layers resulting in larger avalanches.
- Pay attention to overhead hazards like cornices which could trigger the persistent slab.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 21st, 2021 4:00PM
