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Avalanche Forecast

Archived

Dec 6th, 2018–Dec 7th, 2018

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

Regions

Kootenay Boundary.

Conditions have been steadily improving. If you're looking for trouble, you might still find it around steeper, protected solar aspects where surface hoar coexists with a sun crust.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Thursday night: Cloudy with clear periods. Light southwest winds.Friday: A mix of sun and cloud. Light southwest winds. Alpine high temperatures around -8, slightly cooler at lower elevations under a mild temperature inversion.Saturday: Mainly cloudy. Light southwest winds. Alpine high temperatures around -7, cooler at lower elevations with a lingering mild temperature inversion.Sunday: Mainly cloudy with thicker low level cloud. Light south winds, increasing to strong at alpine elevations. Alpine high temperatures around -4, cooler at lower elevations under a more pronounced temperature inversion.

Avalanche Summary

Several small natural wind slab releases were observed in the Whitewater area on Wednesday. These occurred on steep alpine features and may have been a product of recent northerly winds. Big thanks go out to our contributors to the Mountain Information Network. Please continue to post your observations here.

Snowpack Summary

Days of cold temperatures and increasingly clear skies have been growing a new layer of feathery surface hoar on the surface. Winds may have scoured some of this surface hoar from alpine slopes. The cold has also been transforming our roughly 20 cm of aging storm snow on the surface into a layer of faceted (weak, sugary) snow. At treeline, the height of snow is between about 100 and 140 cm. At 50 to 70 cm below the surface, there is a closely stacked pair of buried persistent weak layers. The upper layer consists of surface hoar (feathery crystals) in most places, but may present as a sun crust on steep south facing slopes. The deeper layer features similar surface hoar distribution over a more widespread temperature crust. These layers have shown ongoing but variable reactivity in snowpack tests in the past week. Both surface hoar layers are thought to be widespread at treeline and may also extend into sheltered alpine features.At the base of the snowpack is a thick melt-freeze crust that formed near the end of October. Observations of reactivity at this crust have been limited, but it has acted as the failure plane in several large avalanches in the neighbouring South Columbias.

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.