Avalanche Forecast
Issued: Dec 20th, 2019 8:00AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Persistent Slabs and Deep Persistent Slabs.
percy woods,
Parks Canada
High Avalanche Danger today through Saturday! A great day to avoid avalanche terrain.
Summary
Weather Forecast
An atmospheric river of moisture from the Pacific has begun to dump on the Selkirks. The forecast calls for 30cm in the next 24 hours with an additional 20cm through the day Saturday. Moderate to strong SW winds will accompany this storm front accompanied by freezing levels rising to 1500m. The storm should abate late Saturday.
Snowpack Summary
Field tests and observations found a reactive storm slab down 20cm. 80cm+ of snow now buries the Dec 11 surface hoar layer. Previous new snow, and mod winds built storm slabs at all elevations. The Nov 23rd surface hoar/crust/facet combo is down +/-130cm has become increasingly stubborn in testing. These interfaces are expected to wake up today.
Avalanche Summary
A fresh avalanche cycle began last night at 10pm and is ongoing. We expect a widespread avalanche cycle to continue at all elevations through to Saturday afternoon when the winter storm is forecast to abate.
Confidence
Problems
Storm Slabs
A touchy storm slab formed Dec 19 over a Stellar layer down 30cm. This layer is expected to be widespread and sensitive to human triggering.
- Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
- The new snow will require several days to settle and stabilize.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
The Dec 11th Surface Hoar(SH), size 5-12mm is down 80cm+. This sliding layer is expected to wake up tomorrow naturally when storm slab releases overload it. This will result in large avalanches likely running to valley bottom.
- Use conservative route selection, choose moderate angled and supported terrain with low consequence.
- If triggered the storm slabs may step down to deeper layers resulting in large avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
The Nov 15 melt freeze crust is down deep in the snowpack. This layer may reach threshold for overload from avalanches triggered in upper snowpack layers. The resulting avalanches will be large.
- 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 21st, 2019 8:00AM
