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

Regions

Purcells.

Confidence

Fair - Forecast snowfall amounts are uncertain on Tuesday

Weather Forecast

Overnight and Monday: Strong Northwest winds with 2-3 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 1000 metres.Tuesday: A warm pulse of moisture is expected to bring 5-10 cms to elevations above 1200 metres with strong Southwest winds.Wednesday: Light Southwest winds and another 3-5 cms with freezing levels rising back up to about 1100 metres.

Avalanche Summary

Some pockets of wind slab up to size 1.5 were reported, and sluffing up to size 1.0 continues to be reported from steep terrain.

Snowpack Summary

Wind slabs continue to develop in the alpine and at treeline. Forecast strong Northwest winds are expected to further develop these wind slabs. The recent storm slab continues to be reactive down 30-50 cms at treeline and below. Below freezing temperatures overnight have helped to strengthen the moist surface layers that developed during the weekend warm period. Rising freezing levels forecast during the next pulse of moisture may weaken the old storm slab at lower elevations. The mid-pack is well settled and there are no reported deep layers of concern.

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.