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Avalanche Forecast

Archived

Mar 5th, 2017–Mar 6th, 2017

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

Regions

Little Yoho.

Avalanche control on Mt Bosworth (March 6,2017), no backcountry recreation in this area.

A reactive storm slab has produced large avalanches through the forecast region.

Weather Forecast

Flurries are expected through to Tuesday with 5-10cm of snow accumulation, light to moderate winds from the west will continue and temperatures will remain below freezing.

Snowpack Summary

20-40cm from the past storm with less in the western parts of the forecast region. This new snow has developed a reactive storm slab overlaying a supportive mid pack. In thin areas the lower snowpack is weak, consisting of facets and depth hoar.

Avalanche Summary

Reports of natural avalanches to size 2.5 initiating from storm slabs at alpine and tree line elevations. In isolated cases these avalanches have stepped down to the deep persistent problem. In neighboring forecast regions, remote triggered avalanches have occurred on the storm slab by skiers and explosives.

Confidence

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.