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Avalanche Forecast

Archived

Nov 30th, 2017–Dec 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 Coastal.

The recent stormy weather has dumped as much as 110 cm of new snow on last week's crust. This has created reactive storm slabs and there have been reports of large avalanches. Use a conservative approach and terrain selection.

Confidence

Low - Due to the number and quality of field observations

Weather Forecast

Friday: Snow amounts 5-15 cm with moderate South West wind. Alpine temperature -5. Freezing level 500 m and dropping.Saturday: Snow amounts 5-10 cm with light to moderate South West wind. Alpine temperature -7. Freezing level valley bottom.Sunday: Mix of sun and cloud. Light to moderate North West wind. Alpine temperature -7. Freezing level valley bottom. Visit the Mountain Weather Forecast for more details.

Avalanche Summary

No recent natural avalanche activity has been reported. On Wednesday, an explosive triggered slab avalanche was reported up to size 2.5 in the alpine. The aspect is unknown. Earlier in the week, observations from the Shames area reported audible avalanches from across the valley and shooting cracks within the recent storm snow. The recent storm snow will likely take time to settle and bond. Travel in avalanche terrain will require conservative route selection and terrain choices. Please send your recent observations to the Mountain Information Network. Give info get info.

Snowpack Summary

Snow accumulations of 80-100 cm of storm snow in the southern part of the region now lies on the supportive 5-10 cm thick, November 23 rain crust from last week. Winds associated with the new snow has formed reactive wind slabs on leeward slopes. Below this crust is a weak layer that formed in late October and is now buried 120-160 cm within the snowpack. Beneath this October crust is a 20-30 cm thick layer consisting of several thin crusts and facets (sugary snow). Recent snowpack tests and observations indicate that that the new snow is likely reactive to rider triggers.Reports further north near Ningunsaw, describe a much shallower facetted snowpack 60-120 cm.

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.

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.