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Avalanche Forecast

Archived

Nov 30th, 2012–Dec 1st, 2012

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Kootenay Boundary.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain for the entire period

Weather Forecast

Saturday: Moderate to heavy snowfall / Moderate southwest winds with strong gusts / Freezing level at 1500mSunday: Light snowfall / Light southeasterly winds / Freezing level @ 1300m Monday: Light to moderate snowfall / Moderate to strong southwesterly winds / Freezing level @ 1200m

Avalanche Summary

On Friday there were reports of natural and skier triggered slab avalanches to size 1.5 in the Kootenay Pass area. They occurred on north aspects and are suspected to have run on the November 28th surface hoar.

Snowpack Summary

Recent snowfall accumulations across the region have been highly variable; however, as of Friday some areas had upwards of 30cm overlying a variety of surfaces which may include weak surface hoar crystals, a sun crust on steep solar aspects, and well settled storm snow from last week. Forecast wind and snow will add to the size and reactivity of this developing slabIn the mid snowpack there may be a spotty, thin buried surface hoar layer between 50 and 80cm down. At the base of the snowpack sits the early November rain crust. Located about 100cm below the surface, it seems most likely to be found in deeper snowpack areas and may have associated facets. These layers seem to have been unreactive in recent days, but may have the potential to 'wake-up' with forecast loading.In general, snowpack data is sparse in this region and significant variations likely exist from one drainage to another. In short, digging down and making your own observations will be critical to safe slope selection. Any observations from the field are welcome at [email protected].

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.