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Avalanche Forecast

Archived

Jan 1st, 2012–Jan 2nd, 2012

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

Regions

South Columbia.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain

Weather Forecast

Warm air enters the region late Sunday persisting through mid-day Monday. Freezing levels are forecast to be between 1500 - 2000 m & winds in the alpine will be ripping out of SW @ 55 -95 k/hr A cold front moves in after lunch Monday lowering freezing levels and bringing light snowfall, 5 cm or so are expected Monday night. A weak ridge builds in Tuesday AM before a more organized low moves in Tuesday afternoon into Wednesday. We can expect 15 - 20 cm before the system exits to the east Wednesday afternoon.

Avalanche Summary

Many small natural avalanches confined to the new snow have been reported from the region. While important to note, the bigger story is the continued activity on the mid-December surface hoar/facet/crust layer. Remote triggering (setting off avalanches from afar) continues to be reported. The bottom line is that this layer is still sensitive to the weight of a skier or sledder. It's also significant that avalanches failing on this layer are being reported in areas users often consider safe, such as moderately angled slopes near treeline. Large loads produced avalanches to size 3 (big enough to bury/destroy a car) in the region Saturday.

Snowpack Summary

80 - 120cm of total storm snow has fallen in the region since Christmas. Winds have redistributed the storm snow into wind slabs that are quite widespread; you can find them at and above treeline in wind exposed locations. Even open areas below treeline are suspect for wind affected snow. A surface hoar/facet/crust interface (persistent weakness aka PWL) from mid-December is buried anywhere from 80-120cm deep & has been quite reactive making for touchy avalanche conditions.

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.