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Avalanche Forecast

Archived

Mar 17th, 2014–Mar 18th, 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

Tuesday: Mainly cloudy with a chance of flurries – around 5 cm. The freezing level is around 1500 m. Ridge winds are moderate from the W-SW. Wednesday: Periods of snow – 10-20 cm. The freezing level is near 1300 m and ridge winds are moderate from the West. Thursday: Cloudy with flurries and sunny breaks. The freezing level is around 1000 m and ridge winds are light.

Avalanche Summary

On Sunday a few small natural avalanches were reported in steep alpine terrain. Skier and explosive control work also produced numerous size 1-2 soft slabs, primarily from wind loaded slopes at or above treeline. On Friday there was also a report of a size two avalanche that was triggered accidently on a North facing slope at treeline on the early March surface hoar/crust combo. 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

Another 10-15 cm of new snow brings the total recent storm snow total to 40-60 cm. Periods of strong westerly winds have created fresh wind slabs in exposed lee and cross-loaded terrain. The new snow sits on a crust in most places, which may also be mixed in with surface hoar in some areas. The early March interface, 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 below the snow surface and widespread throughout the region. Surface avalanches in motion and cornice fall still 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.