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Avalanche Forecast

Archived

Apr 18th, 2014–Apr 19th, 2014

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

Regions

South Rockies.

Check out this video by the CAC South Rockies field team describing current conditions and what to expect in the South Rockies and Lizard Range over the next couple of weeks. Please send us your observations at [email protected]

Confidence

Poor - Due to the number of field observations

Weather Forecast

Saturday: A mix of sun and cloud. The freezing level rises to around 2000-2200 m and ridge winds are moderate to strong from the S-SW. Sunday: Sunny with cloudy periods and possible flurries. The freezing level is around 1800-2000 m and ridge winds are moderate from the west.Monday: Cloudy with sunny breaks. The freezing level jumps up to around 2500 m. Wind are moderate from the S-SW.

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

Recent snowfall amounts probably vary throughout the region but I would expect there is around 15-30 cm in most places. The snow line has probably hovered between 1500 and 1700 m. The new snow is sitting on hard crust and may not bond well initially. Higher north aspects may have as much as 50 cm of settling dry powder. It looks like we should see cool temperatures overnight which will likely form a new surface crust at lower elevations. 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

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.

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.

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.