Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Dec 20th, 2011–Dec 21st, 2011

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Purcells.

Confidence

Fair - Due to variable snopack conditions

Weather Forecast

Wednesday: Mostly dry. Light northerly winds. Alpine temperatures around -12C. Thursday: Dry. Winds becoming westerly. Remaining cold, but a mild inversion could locally elevate alpine temperatures by a few degrees. Friday: light snowfall with around 2 cm expected. Moderate NW winds. Alpine temperatures around -12C.

Avalanche Summary

A natural avalanche cycle up to size 2 occurred in the Dogtooth and Bugaboo ranges last weekend. Human-triggered slab avalanches have been reported subsequently from these areas up to size 2 on a variety of aspects and elevations. Due to the well-developed nature of the surface hoar layer, touchy avalanche conditions will persist where the slab is sufficiently deep and avalanches have not already run.

Snowpack Summary

The Purcell region has been getting less snow in the recent storms than the Selkirks. This means in many areas we have not reached critical threshold on a layer of large surface hoar and near surface facets that was buried mid-December. Exceptions to this are the Dogtooth range and Bugaboos, where avalanches to size 2 have been releasing on this layer with fracture depths of 20-30 cm. Typically, the mid-December surface hoar layer currently lies about 20 cm below the snow surface. Some areas have a sun crust in the alpine on steep south and west aspects. There is a rain crust that is buried between 40 to 55 cm in some areas that reaches up to about 2200 m. Lower in the snowpack, the mid-layers are well-consolidated and strong. Near the base of the snowpack there are a few layers that have the potential to wake up with a really big storm or very heavy loads. These include a surface hoar layer from early November, a crust/facet combo from October and the interface on steep glaciated terrain with snow that did not melt over the summer.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.