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Avalanche Forecast

Archived

Dec 25th, 2011–Dec 26th, 2011

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 and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

South Columbia.

The forecaster blog has great information on the current conditions and some ideas on how to manage terrain. Check it out!

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Monday: Expect mixed skies with flurries building later in the day. Accumulations could be higher over the western slopes/west facing terrain. West winds with temperatures reaching -7. Tuesday &Wednesday: We should see a lull in the precip in the morning and then flurries through the afternoon, evening and into Wednesday. Freezing levels will slowly rise from 1000-2000m under continued westerly winds.

Avalanche Summary

There are reports of natural, human and remote triggered avalanches up to size 1.5. While previous avalanches were confined to the northern part of the region, these new reports are from further south. The focus is on elevations between 1500-2100m. While small, these new avalanches suggest that the tipping point for activity on the early December surface hoar is slowly arriving, and the problem is likely to get worse as more snow falls.

Snowpack Summary

As much as 20cm of new snow has fallen in the most recent storm pulse. This overlies soft slabs on North through East aspects and some spotty, small surface hoar/surface facets in sheltered locations at treeline and below. This brings the total load over the early December surface hoar to 35cm in the South and 65cm in the North. This surface hoar layer is still producing sudden results in stability tests and a whole block rutchblock 4 was also observed. This is certainly the layer to watch; check out the forecaster blog for more info/ideas on this current problem. The midpack is well consolidated and strong.

Problems

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.

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.