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Avalanche Forecast

Archived

Jan 31st, 2017–Feb 1st, 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 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.

Regions

Northwest Inland.

The load over the deep persistent slab problem in parts of the region has reached a critical level. Triggering a full depth of snowpack avalanche is possible. For more details, click here for the latest Forecaster Blog post.

Confidence

Moderate -

Weather Forecast

Clear skies are expected for Wednesday and Thursday with increased cloud forecast for Friday. Ridgetop winds should remain generally light to moderate from the east for Wednesday and Thursday, and then become stronger on Friday. Freezing levels should remain at valley bottom for the forecast period.

Avalanche Summary

On Sunday there were several skier, snowmobile and naturally triggered avalanches to report from riding areas to the west of Smithers. One of these avalanches in the Microwave area involved the full depth of the snowpack and resulted in a full burial. Click here for a description and images of the incident on Facebook. It is well worth a read. Another report in the Ashman area shows a skier-triggered size 2 avalanche running on surface hoar at the storm snow and old snow interface in a sheltered area at tree line. Natural avalanches are reported to be full depth of the snowpack to size 3.5 in the alpine and at tree line.

Snowpack Summary

A series of snowfalls last week accumulated 40-80 cm of storm snow, which now sits above a widespread rain crust up to about 1300 m. At tree line and above, the storm snow is settling and/or being redistributed into new wind slabs. Below, several buried surface hoar layers can be found, between 50-100 cm deep. Before the storm, these layers had been yielding moderate to hard results in snowpack tests. A generally stiff mid pack sits above weak sugary snow near the ground. The new load sitting on top has reached a critical level and has woken-up a deep persistent slab problem in many parts of the region. The consequences of triggering an avalanche on this layer are high. This is a good time to be very cautious and disciplined with terrain choices.

Problems

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.

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.