Avalanche Forecast
Issued: Dec 17th, 2020 8:12AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Loose Dry and Persistent Slabs.
Percy Woods,
All winter permit areas are closed today. We are in a period of prolonged storm with increasing avalanche danger.
Summary
Weather Forecast
Flurries today with accumulations around 6cm.
Alpine temperature: High -6 °C.
Ridge wind west: 30-45 km/h.
Freezing level: 1300 metres.
Friday periods of snow accompanied by strong SW winds, with accumulations around 20cm.
Saturday the storm cycle continues with another 10cm cooling temps and strong SW winds.
Snowpack Summary
10cm+/- of new snow brings our storm total to ~50cm in the last 72hours. Mod S-SW winds and mild temperatures are forming soft storm slabs at all elevations. Weak layers; Dec 13 Surface Hoar and Dec 7 crust/Surface Hoar are in the top 60cm. Deeper in the snowpack the Nov 5th crust is currently unreactive to stability tests or skiers.
Avalanche Summary
A skier went for a ride in a size 1.5 slab avalanche below treeline yesterday. They were uninjured. Numerous avalanches to size 3 along the highway corridor yesterday morning. Of note were slab releases initiating at below treeline elevations. Winds are picking up this morning with corresponding new avalanche activity.
Confidence
Problems
Storm Slabs
Storm snow totals are eclipsing 50cm in the last 72 hours at Treeline. Mod S-SW winds and mild temperatures have formed storm slabs at all elevations. Storm slabs are failing on the Dec 13th Surface Hoar Layer.
- Watch for whumpfing, hollow sounds, and shooting cracks.
- Use conservative route selection, choose moderate angled and supported terrain with low consequence.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Loose Dry
Sluffing continues to be a concern with significant amounts of new snow over the last 48 hours. Loose dry avalanches will have enough mass to push riders around in steep terrain. Extra care is required around cliffs and confined gullies.
- Use conservative route selection, choose moderate angled and supported terrain with low consequence.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
70cm sits on the Dec 7th weak interface of rain crust/sun crust/surface hoar combo. Our new storm slab could easily step down to this interface, significantly increasing the size and destructive potential.
- If triggered the storm slabs may step down to deeper layers resulting in large avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 18th, 2020 8:00AM
