Avalanche Forecast

Archived

Mar 8th, 2013–Mar 9th, 2013

Alpine

Natural avalanches possible, human triggered probable.

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.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Kootenay Boundary.

Confidence

Poor - Timing, track, or intensity of incoming weather is uncertain on Sunday

Weather Forecast

Friday night and Saturday: The dominating feature is a ridge of high pressure over the whole province bringing warmer air (-1 in the alpine), freezing levels rising to 1700 m., clear skies and light NW winds. Sunday: The ridge is breaking down in the North and remains in the Southern part of the interior range. There is a chance of light precipitation for Sunday (5-10 mm) with winds picking up in the moderate range from the W. Temperatures are slightly cooler than Saturday.Monday: Another system which could deliver more precipitation is expected for Monday but the timing and intensity is still uncertain.

Avalanche Summary

Several soft slabs size 1 and 1.5 were triggered by skiers in the new snow (20-30 cm deep) and was running on the underlying crust or on the older snow interface. There was also several reports of sluffing in steep terrain.

Snowpack Summary

Warm temperatures and solar radiation forecasted for tomorrow will weaken the surface layer possibly triggering the recent storm slab (between 20-30 cm deep). This recent snow is sitting on an older snow interface above 2000 m. and on a melt freeze crust below that elevation. In much of the region, up to 80 cm snow overlies fairly well preserved surface hoar and sun crust. This interface is still producing sudden collapse results during snow tests. A cornice fall or an avalanche in the storm snow could definitely trigger this deeper instability, especially where the melt freeze crust does not exist above 2000 m.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.