Avalanche Forecast
Issued: Apr 16th, 2017 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Cornices and Persistent Slabs.
tim haggarty,
Avalanche Canada
Wind and storm slabs in the alpine continue to react to skier traffic today.
Summary
Weather Forecast
Clear skies will lead to a solid freeze overnight Sunday. Despite the potential for flurries Monday, freezing levels are still forecast to reach 2200m as unsettled air tracks east from the coast: don't rule out loose wet activity and light rain BTL. Tuesday should see West winds return to the moderate range with the potential for flurries.
Snowpack Summary
Sunday morning saw 5 to 10cm storm snow over recent crusts below 2300m. Solar heating is making new crusts today. 20-50cm of snow over the last week in the alpine sits over crusts on S aspects and was redistributed by moderate west winds. At tree line and above the mid-pack is a 120cm+ firm slab overlying weaker basal facets in much of the region.
Avalanche Summary
Skiers triggered a sz 2 slab at 2500m on the S aspect of Mt Jimmy Simpson 40 deep over a crust on a 30 degree slope. A field team on the Wapta reported sz 2 windslabs: 1 on the SE aspect of Mt Ayesha, and 2 on the East aspect of Arete Peak, an icefall triggered sz 2 slab off of the East aspect of Mt. Collie, and sz 1.5 loose wet off the S of Gordon
Confidence
Problems
Wind Slabs
Moderate to strong west winds created fresh slabs and widespread wind effect in the alpine Friday redistributing up to 40 cm of recent snow. Use caution on solar slopes as well where this recent snow is bonding poorly to crusts.
- If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.
- The recent snow is now hiding windslabs that were easily visible before the snow fell.
Aspects: North, North East, East, South East, South, South West.
Elevations: Alpine.
Likelihood
Expected Size
Cornices
These saw rapid growth until winds died down Sunday morning. Minimize your time underneath these and remember that a cornice failure could also trigger the deep persistent slab on the basal facets.
- Avoid travel on slopes that are exposed to cornices overhead.
- Stay well to the windward side of corniced ridges.
Aspects: North, North East, East, South East.
Elevations: Alpine.
Likelihood
Expected Size
Persistent Slabs
The snowpack is gaining strength, however the facets deeper in the snowpack remain a concern in thin alpine areas and where a cornice could trigger the slope. These facets do exist in isolated treeline areas, but are not currently a problem.
- Pay attention to overhead hazards like cornices which could trigger the deep persistent slab.
- Choose the deepest and strongest snowpack areas on your run.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Apr 17th, 2017 4:00PM
