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Avalanche Forecast

Archived

Apr 13th, 2017–Apr 14th, 2017

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

Regions

Little Yoho.

Good ski quality at upper elevations.  The deeper facets could still  be triggered by a cornice or from an unlucky thin spot, so limit overhead exposure and ease into bigger terrain. SH

Weather Forecast

Snow tapering for Friday, with freezing levels down to valley bottom overnight, and up to 1800m in the afternoon.  Winds will be mainly light and skies mainly cloudy.  A cooling trend is expected through the weekend.

Snowpack Summary

Up to 40cm of snow has fallen in the last few days above 2000m, likely forming isolated storm slabs in the alpine. On solar aspects, this snow is sitting over various sun crusts into the alpine. The lower elevation snowpack has been getting moist in the PM  There are persistent facets in the region, but the snowpack is stronger overall.

Avalanche Summary

No new avalanches were observed or reported on Thursday, but field teams were not in the Little Yoho area.

Confidence

Due to the number of field observations

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

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.