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Avalanche Forecast

Archived

Apr 17th, 2014–Apr 18th, 2014

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
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 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 - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Friday: Cloudy with sunny breaks and scattered showers or flurries (~5-10 cm). The freezing level is around 1800 m. Winds are moderate gusting to strong from the west. Saturday: A mix of sun and cloud and warm! The freezing level rises to 2600 m and ridge winds are moderate to strong from the southwest. Sunday: Cloudy with sunny breaks and a chance of showers. The freezing level rises to 2200-2400 m and ridge winds are moderate from the west.

Avalanche Summary

On Thursday, the CAC field team observed a natural cornice failure which triggered a thin slab below near Window Mountain in the Crowsnest Pass. There were also several loose wet avalanches from steep terrain. The team also saw the remnants of a natural deep persistent slab that broke several large mature trees. This avalanche probably occurred in the past week or so, and most likely during a warming event.

Snowpack Summary

Above around 1800 m the mid and upper snowpack consists of layers of moist snow mixed in with several well bonded crusts, and around 10-15 cm of new snow on top. High north aspects may have around 30 cm of settled storm snow sitting on a crust, possibly more where wind loaded. Warm temperatures and periods of rain have made the snow surface wet below 1800 m, and at low elevations the entire snowpack is probably moist or wet. 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 during sunny periods. 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.

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.