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Avalanche Forecast

Archived

Jan 31st, 2013–Feb 1st, 2013

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

Regions

South Coast.

Confidence

Good

Weather Forecast

The offshore upper ridge will start to move onto the province pushing the polar front to the North bringing rising freezing levels, and sunny skies Friday afternoon into Saturday. Friday: A mild SW flow will show no new precipitation and ridgetop winds will be light from the West. Alpine temperatures will rise to 3.0 degrees and freezing levels will rise to 2200 m.Saturday: Continued warm temperatures and sunny skies. Alpine temperatures will rise to 4.0 degrees and freezing levels will be near 2100 m. Ridgetop winds will be light from the SW.Sunday: Dominating ridge will start breaking down bringing light-moderate precipitation. Alpine temperatures will drop to -4.0 with freezing levels falling to 1200 m.

Avalanche Summary

From the Northern parts of the region, a natural slab avalanche size 2.5 was reported from a East aspect at 2000 m, failing on the buried surface hoar layer from early January. This layer has been fairly quiet recently, goes to show it may still be reactive in isolated areas. Another noted size 2.0 slab avalanche failed on the recent buried weakness from a NNW aspect around 1600 m.Several rider triggered slab avalanches up to size 2.0 have been reported south of the Coquihalla. These avalanches were triggered from SE-E aspects  at 1600-1700 m, failing on the most recently buried crust/surface hoar/facet layer.

Snowpack Summary

Up to 30 cm of snow fell over the past few days with light to moderate winds. This snow seems to be settling and gaining strength although forecast rising alpine temperatures and sunny skies will affect and weaken the upper snowpack. Wind slabs are possible behind ridges and ribs and may be touchy to rider triggers. Wind slabs could also be found in unsuspecting places due to changing winds from NW-SW. Be cautious of cross-loaded terrain features. The new snow has buried a variety of surfaces including old wind slabs, crusts and large surface hoar crystals which can be found in sheltered terrain below treeline. The most recent buried crust/surface hoar down approx. 10-30 cm are producing moderate-sudden planar and resistant test results, and should remain a layer to watch. Down deeper sits another surface hoar layer (40-80 cm) which seems to be gaining strength.Near the base of the snowpack, a crust/facet layer exists, which is now unlikely to be triggered, except perhaps by heavy triggers in unsupported, shallow, rocky terrain where more faceting has taken place.

Problems

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.

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.

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.