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Avalanche Forecast

Archived

Apr 19th, 2014–Apr 20th, 2014

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

Regions

Purcells.

Avalanche danger can quickly rise above what is forecast with warming temperatures and/or brief periods of sun. Be aware of changing conditions and overhead hazards.For more insight into spring danger ratings, check out our Blog Post.

Confidence

Fair - Due to the number of field observations

Weather Forecast

Synopsis:  A weak ridge of high pressure will develop over the interior of the province Sunday.  Convective flurries may be possible.  The ridge shifts eastward as the next system moves in over the region Monday night.Tonight and Sunday: Light precipitation overnight (up to 10cm) then clearing /  Moderate then light westerly winds  / Freezing levels 2000mMonday: Partly cloudy with a chance of flurries /  Moderate southwesterly winds / Freezing levels up to 2600m Tuesday: Flurries (5-20 cm) / Light southerly winds / Freezing levels between 1900 and 2500m

Avalanche Summary

At lower elevations and on solar aspects small to large loose wet avalanche continue to be triggered on steep slopes.  Cornices collapses have been reported during periods of daytime warming.  Occasionally these heavy triggers have caused larger deep slab avalanches on the slopes below.

Snowpack Summary

5-30 cm of recent storms snow is rapidly settling and appears to be bonding well to a supportive crust that can be found on all aspects and elevations except for high elevation north-facing terrain.  Soft winds slabs may be found in the immediate lee of ridges and ribs.Three persistent weak layers still exist in the highly variable snowpack of the Purcells: The mid-March sun crust/surface hoar layer down 50-80cm and the early-March crust/facet/surface hoar layer down around 80-120cm seem to be laying dormant for the time being. The mid-February crust/facet/surface hoar combo is typically down 60 - 120cm. Direct triggering of this layer has become unlikely, however, cornice fall, a smaller avalanche in motion or prolonged warming may wake this layer up.  The resulting avalanche would be very large and destructive.At the base of the snowpack weak basal facets can be found in many areas, however triggering this layer is unlikely.

Problems

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.

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.

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.