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Avalanche Forecast

Archived

Mar 18th, 2017–Mar 19th, 2017

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

Regions

Little Yoho.

Avoid exposure to avalanche terrain: the new storm has resulted in another avalanche cycle today.

Explosive Avalanche Control is planned for Mt Bourgeau, Mt Stephen and Mt Dennis. Please no climbing or skiing in these areas Sunday.

Weather Forecast

A significant storm is underway Saturday with moderate to strong SW winds, moderate precip and freezing levels in excess of 2200m. The storm will taper off Sunday morning and freezing levels are expected to drop back to valley bottom as winds shift back to westerly. A cooling trend will continue with light precip until skies start to clear Monday.

Snowpack Summary

10 to 20cm of new snow, combined with 40 to 80cm from the last 14 days has created a significant load over a fundamentally weak snowpack. Rain to 2200m, warmer overall temperatures, and snow in the alpine combined with strong SW winds are building superficial wind and storm slabs and overloading the deep basal facet layers. Poor travel below 2000m.

Avalanche Summary

Control work yesterday on the 93 S produced surprisingly large results reaching historical runnouts to sz 3.5. Extensive Natural activity has been seen on flights throughout the forecasting region to size 4 with fracture lines longer than 1km in many locations. Reports today indicate new activity to the same scale as the latest storm hits.

Confidence

Timing, track, or intensity of incoming weather system is uncertain on Saturday

Problems

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.

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.