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Avalanche Forecast

Archived

Feb 3rd, 2013–Feb 4th, 2013

Alpine
Natural avalanches unlikely, human triggered possible.
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, 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

South Columbia.

Confidence

Fair - Forecast snowfall amounts are uncertain on Tuesday

Weather Forecast

Overnight and Monday: Strong Westerly winds with 5-10 cms of snow and alpine temperatures down to -8.0. A few cms during the day with gusty Northwest winds and freezing levels rising to about 900 metres.Tuesday: A warm pulse of moisture is expected to bring 10-15 cms to elevations above 1000 metres with strong Southwest winds.Wednesday: Strong Westerly winds and flurries. Freezing level up to 1100 metres during the day.

Avalanche Summary

The sun caused a natural cycle of loose and slab avalanches up size 2.0 that were mostly started in very steep un-skiable terrain. Wind slabs also continued to release naturally or were triggered by skiers. The West Monashee continued to be the most reactive area reported, with natural avalanches up to size 3.5 that were releasing in the recent storm snow.

Snowpack Summary

Wind slabs continue to develop in the alpine and at treeline. A sun crust has developed on steep Southerly aspects, and a melt-freeze crust has developed at lower elevations due to the recent high freezing levels. The recent storm slab continues to be reactive at treeline and below on steep convex slopes that have buried surface hoar at the January 23rd interface (between 40-60 cms down). The mid-pack is well settled and strong. There are a few locations that continue to find a well preserved surface hoar layer from early January that is buried down about 90 cms. Forecast cooler temperatures should help to strengthen the recent storm slab where it became moist at lower elevations.

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.