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Avalanche Forecast

Archived

Nov 30th, 2018–Dec 1st, 2018

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

Regions

North Columbia.

There is a lot of uncertainty with the reactivity of the buried surface hoar layer down 40-80 cm. Human triggered avalanches are more likely at treeline and sheltered locations in the alpine where this weak layer exists. New Forecaster blog HERE.

Confidence

Low - Due to the number of field observations

Weather Forecast

Overnight FRIDAY: Cloudy / Alpine Low -10 / Light, southwest wind / Freezing level valley bottom.SATURDAY: Mostly cloudy / Alpine high -11 / Light, northeast wind / Freezing valley bottom.SUNDAY: Mostly cloudy / Alpine high -11 / Light, northwest wind / Freezing level valley bottom.MONDAY: Mix of sun and cloud / Alpine high -13 / Light, northwest wind / Freezing level valley bottom.

Avalanche Summary

No avalanches were reported in this region on Wednesday. However, we currently have very few observations from within this region. Please post your observations to the Mountain Information Network (MIN). Although not in this region, a notable size 2.5, explosive triggered avalanche was reported south of Revelstoke on Thursday. The avalanche released on the October crust at the bottom of the snowpack in steep, rocky terrain.

Snowpack Summary

Recent storm snow amounts range from 40-80 cm. There may be some lingering wind slaps in exposed, alpine terrain, but the primary concern in the snowpack is a weak layer of surface hoar (feathery crystals) and/or sun crust depending on the aspect of the terrain. This layer is below the recent storm snow and is down roughly 30-70 cm. The surface hoar is most pronounced at treeline, but it may be found in sheltered, north facing alpine areas.At the base of the snowpack is a crust that formed in late October. There have been no recent reports in this region of reactivity on this layer. However, the South Columbia region has had two large avalanches on this layer, one triggered by a snowmobile and the other a bomb. Steep, rocky terrain, with a shallow snowpack are the most likely areas to trigger this layer.Total snowpack depths vary greatly with elevation. Recent reports show depths of 120-210cm in the alpine, 80-150 cm at treeline and 10-120 cm below treeline.

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.