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Avalanche Forecast

Archived

Apr 16th, 2014–Apr 17th, 2014

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

This bulletin was created using very limited field data. If you are out in the mountains, please send your observations to [email protected]

Confidence

Poor - Due to the number of field observations

Weather Forecast

Tonight and Thursday: Cloudy with showers or flurries – trace tonight, 5 cm/mm Thursday. The freezing level is around 2200 m. Winds are moderate from the South.  Friday: Cloudy with flurries or showers and isolated sunny breaks. The freezing level is around 1800 m. Winds are moderate and gusty from the W-NW.  Saturday: Cloudy with sunny periods and a chance of showers. The freezing level rises to 2300 m and ridge winds are light to moderate from the south.

Avalanche Summary

No new avalanche activity was reported on Monday or Tuesday. Most of the recent reported activity has been limited to loose wet slides and cornice collapses from warming and solar radiation.

Snowpack Summary

Up to 5 cm of new snow sits on a solid and thick melt-freeze crust above 1500 m. High high north aspects may have 15-30 cm of dry snow sitting on a previous crust, and possibly more where wind loaded. Warm temperatures and periods of sun will likely create moist or wet surface snow and may soften the underlying crust. The mid and upper snowpack consists of a mix of moist snow and well bonded crusts. The deep facet/crust persistent weakness buried at the beginning of February (now down up to 80-100+ cm) should stay on your radar, especially on all alpine slopes that will see the intense sun tomorrow. Any activity at this interface would be large and destructive. Also, give large sagging cornices a wide berth when traveling on or below corniced ridges.

Problems

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.