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Avalanche Forecast

Archived

Feb 24th, 2013–Feb 25th, 2013

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

Regions

South Columbia.

Confidence

Fair - Intensity of incoming weather is uncertain on Sunday

Weather Forecast

Sunday night and Monday: Heavy snowfall becoming light on Monday / Strong west winds becoming light northwesterly on Monday / Freezing level at 800mTuesday: Mix of sun and cloud / Light southwest winds / Freezing level at 1000mWednesday: Light snowfall / Light southwest winds / Freezing level at 900m

Avalanche Summary

Revelstoke RCMP confirm one skier has been killed in an avalanche which occurred in the Greely Lake area, well outside of the controlled area boundaries of the Revelstoke Mountain Resort on Friday afternoon. For more details on the incident, please follow this link: Incident ReportElsewhere in the region many avalanches to size 2.5 were observed on a variety of aspects and elevations. They occurred in response to intense wind and heavy snowfall on Friday. Avalanches in this cycle ran as loose dry and storm slab avalanches, while many failed at the persistent February 12th interface.Storm snow instabilities are expected to ramp up again on Sunday night with forecast weather.

Snowpack Summary

Up to 60cm of recent snow and wind created potent new storm slabs which seem to be most reactive in wind-exposed terrain. These heavy accumulations add to the 30 to 60cm of snow which overlie the weak surface hoar layer which was buried on February 12th. The additional weight of the new snow and wind affect is expected to add reactivity to this persistent weakness which remains a primary concern for professionals in the region. This interface has also shown reactivity on southerly aspects where a sun crust formed during the period from February 8th-11th. The mid to lower snowpack are generally strong and well settled. I would expect significant cornice growth with the current weather pattern, and expect them to be weak and potentially destructive.

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.