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Avalanche Forecast

Archived

Dec 11th, 2013–Dec 12th, 2013

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

Regions

South Rockies.

Confidence

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

Weather Forecast

The South Rockies will begin to see mostly light amounts of new snow, gradual warming and strong ridgetop winds as the weakening cold front passes through on Thursday. Thursday: Cloudy with some flurries. Alpine temperatures near -8. Ridgetop winds moderate from the SW.Friday: Precipitation will taper off as we see a break in the system. Cloudy skies, a trace of new snow. Alpine temperatures -7. Ridgetop winds moderate from the SW.Saturday: Cloudy with snow amounts 5-10 cm. Alpine temperatures -4. Ridgetop winds moderate from the SW gusting to 100 km/hr.

Avalanche Summary

No new avalanche observations have been reported, however I suspect that wind slabs may be easily rider triggered. Use extra caution on cross-loaded slopes, and in the immediate lee of ridgelines. Small loose dry avalanches are likely from steeper slopes, and do not support a significant problem unless you were pushed into a terrain trap like a cliff, or a gully.

Snowpack Summary

Incremental snowfall amounts have begun to bury surface hoar and a faceted upper snowpack. Snowpack depths at treeline seem to vary from 50 - 110 cm and widespread wind effect is noticeable in the alpine and at treeline.Down 30-40 cm sits a surface hoar/ facet/ crust interface. Snowpack testing showed easy results and some whumphing (failure of a weak layer below your feet). If you're seeing or feeling this, consider it a direct indicator of a buried weakness below.Near the base of the snowpack, weak sugary facets and depth hoar exist. This layer may be stubborn to trigger, especially in deeper snowpack areas. In shallower locations the likelihood may increase especially on a steep, convex slope.In some areas it is below threshold below treeline, and early season hazards like open creeks, and stumps exist.

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.