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Avalanche Forecast

Archived

Dec 17th, 2011–Dec 18th, 2011

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

Regions

Northwest Inland.

Confidence

Fair - Intensity of incoming weather is uncertain on Monday

Weather Forecast

Mostly clear skies are forecast for sunday morning with freezing levels at or near surface. Late in the day another frontal system will hit the region bringing 10-15cm of snow overnight and throughout monday. Moderate to strong southwest winds and freezing levels of 900m will accompany this system.Tuesday calls for light to moderate snowfall in the morning, cooler temperatures and reduced westerly winds.

Avalanche Summary

No new avalanches have been reported. This may speak more to lack of reports from the field than actual avalanche conditions. Any information (professional or recreational) from the field is highly appreciated. Please send your observations to [email protected].

Snowpack Summary

About 15 centimetres of new snow and surface hoar crystals are sitting on the less recent 20cm of storm snow which fell earlier in the week. This storm snow we received earlier this week sits on a variety of old weak snow surfaces including surface hoar, melt-freeze crusts and facetted snow. For the most part all aspects between 900m-2000m have a hard melt freeze crust. This crust is widespread and is lingering in most start zones. This is the layer of concern at the moment. Above this crust surface hoar (feathery crystals) and facets (sugary crystals) may be preserved. The recent winds in the alpine seem to have destroyed the surface hoar in exposed areas in the alpine eliminating that problem but creating a wind slab problem. In short, the upper snowpack is variable and a cautious approach is required as new slabs continue to form over the buried weak layers. The midpack seems to be well settled and strong.

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.

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.