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Avalanche Forecast

Archived

Jan 13th, 2013–Jan 14th, 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 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 possible, human triggered probable.

Regions

South Columbia.

Increasing hazard is tied directly to the forecasted warm up. See the forecasters blog for some ideas about the changing situation.

Confidence

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

Weather Forecast

Sunday night and Monday: The ridge of high pressure that has brought cold temperatures lately is being replaced by a warm front pushing in the interior during the day Monday making temperatures warm up in the alpine and leaving some trace of precipitation during the day. Freezing levels will also rise (700) with a possibility of inversion that could keep the peaks closer to zero degrees as well. Cloud cover should also dissipate in the alpine with some mid-level clouds. Winds are forecasted to be moderate from the Northwest.Tuesday: Similar situation for Tuesday with alpine temperatures being well above normal and strong sun radiation and valley clouds. Winds are expected to be moderate from the Northwest.Wednesday:  Similar outlook for Wednesday with dry conditions and high freezing levels and light West winds.

Avalanche Summary

A few size 1 skier triggered slab avalanches were reported from the South part of the region. Except some sluffing in steep terrain, no other reports since last week's avalanche cycle.

Snowpack Summary

The upper snowpack instabilities that were starting to settle could become unstable again if rapid warming occurs in the next 2 days.  Read the forecaster blog to learn more about this process. The 50-90 cm of snow that fell in the past week is sitting over weaker snow surfaces including surface hoar (found especially at and below treeline in sheltered areas), a sun crust (on steep S to SW -facing slopes) and facets. The distribution of buried surface hoar is patchy, but where it exists, it may become touchy again. Recent winds have also left wind slabs in the lee of terrain breaks such as ridges and ribs at alpine and treeline elevations. In areas sheltered from the wind, fast-moving sluff could throw you off your feet or carry you into a terrain trap. A strong mid-pack overlies a weak facet/crust layer near the base of the snowpack, which is now considered inactive.

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.