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Avalanche Forecast

Archived

Mar 18th, 2014–Mar 19th, 2014

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

Regions

South Columbia.

Confidence

Fair

Weather Forecast

Wednesday: Periods of snow – 10-15 cm. The freezing level is near 1000-1200 m and ridge winds are moderate from the W-SW. Thursday: Cloudy with flurries and sunny breaks. The freezing level is around 800 m and ridge winds are light from the NW. Friday: A mix of sun and cloud. The freezing level is around 800 m and ridge winds are light from the NW.

Avalanche Summary

Gusty northwest winds appeared to trigger a few fresh wind slabs from steep lee slopes on Monday. There was also a report of a size 3 natural slab avalanche from a steep south aspect that released on the Feb. 10 layer. This slide occurred during a brief sunny break and sympathetically triggered another size 2.5 on a nearby slope. Last Saturday's avalanche fatality occurred in the Keefer Lake area northeast of Cherryville. The avalanche, which occurred in a cut block at about 1700m, involved 3 sledders who were in a party of 6. Two of the men were able to inflate their airbags and were partially buried. The deceased was reportedly not able to inflate his airbag, and was buried approximately 5m below the surface

Snowpack Summary

Periods of strong westerly winds have created fresh wind slabs in exposed lee and cross-loaded terrain. Around 40-60 cm of recent storm snow sits on a crust in most places, which may also be mixed in with surface hoar in some areas. Weaknesses have been observed within the storm snow and at the interface with this layer. The early March weak layer, which is primarily surface hoar in sheltered areas and a sun crust on solar aspects, is now down 90-120 cm. The February 10th surface hoar/facet/crust combo is 120cm - 200cm deep and is widespread throughout the region. Heavy triggers like a surface avalanche in motion or a cornice fall have the potential to initiate an avalanche on this deeply buried weak layer. An avalanche releasing on one of the deeper persistent weak layers would be very large and dangerous!

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.