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Avalanche Forecast

Archived

Nov 23rd, 2013–Nov 24th, 2013

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

Regions

South Columbia.

Forecast produced with limited field observations.  If you're in the field, please send any information to:[email protected]

Confidence

Fair - Due to the number and quality of field observations

Weather Forecast

Cool temps will give way to gradual warming for the forecast period with freezing levels going up to 3000 M in the next few days. No significant precipitation is in the forecast for the next 7 days. Winds are expected to be generally light to moderate for the forecast period.

Avalanche Summary

High winds accompanying the last significant snowfall produced wind slabs in exposed alpine and tree line locations producing avalanches up to size 3. Rising temps may produce wet sloughs on steep S facing alpine slopes and could trigger deeper instabilities

Snowpack Summary

Recent storm snow is settling and will gain strength with time and warming temps. Wind slabs linger in lee terrain. Surface hoar buried in early November exists in the mid snowpack but due to a lack of data little is known about its reactivity. The October crust/facet interface buried in the lower snowpack will likely be of concern for the foreseeable future. Valley fog and cold clear temps are producing a new surface hoar layer at fog levels and in sheltered north aspects.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.