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Avalanche Forecast

Archived

Mar 17th, 2017–Mar 18th, 2017

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

Regions

Little Yoho.

Another storm on the way will keep the danger ratings elevated through the weekend. Avoid avalanche terrain.

Weather Forecast

Another pulse of snow coming through Saturday although forecast amounts have shrunk somewhat. Expect 20 to 30cm with moderate to strong alpine winds and freezing levels to 2000m. This means rain will fall at lower elevations. On Sunday precipitation will taper off with moderate alpine winds and temperatures will drop off to -15 to 18C.

Snowpack Summary

30-60cm of recent snow and wind have continued to build significant load over midpack facets. The mix of previous rain, warm temperatures, and this new snow is overloading buried storm and windslabs, as well as the deeper facet layers which have woken up. Cooling Friday slowed the natural cycle, but only just. 

Avalanche Summary

Many avalanches up to size 4 in the past 3 days on all aspects and elevations, in many cases reaching historical maximums .  Avalanche control on Hwy. 93 South produced results to size 3.5 showing it is still extremely sensitive. 

Confidence

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.