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Avalanche Forecast

Archived

Nov 30th, 2014–Dec 1st, 2014

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

Regions

Sea To Sky.

Little change expected in the danger ratings until the next storm.

Confidence

Poor - Due to the number and quality of field observations

Weather Forecast

Some cloud over night with very little or no precipitation and moderate Southwest winds. Cold overnight temperatures around -15 in the alpine. Clearing during the day Monday with slightly warmer alpine temperatures around -10 combined with moderate Northwest winds. Tuesday mostly clear with alpine temperatures around -5. Some moisture starting to enter the picture by Thursday.

Avalanche Summary

A skier triggered a size 1.0 wind slab near treeline on a convex slope in the Whistler backcountry. No other reports from this region.

Snowpack Summary

Surface hoar and near surface facets are reported to be growing during the cold and clear weather. Strong Northeast outflow winds developed windslabs 10-40 cm deep since Friday. Heavy precipitation gave way to clearing skies and rapidly cooling temperatures early on Friday morning. Most areas saw heavy rain up to at least 2000 m this week. Above this it's possible that dense storm slabs and fresh cornices formed. Where it did rain, the snowpack is probably frozen solid with a dusting of fresh snow on top. The lower elevation snowpack has also thinned significantly. A weak layer of facetted snow on a crust was buried around 50-60 cm deep before the rain. This weakness may have been flushed out or may now be bridged by a solid ice crust; however, there is no new info on this interface so it would be wise to investigate its existence and strength before venturing into bigger terrain.

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.

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.