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Avalanche Forecast

Archived

Nov 18th, 2011–Nov 19th, 2011

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

Regions

Northwest Coastal.

This bulletin is based on limited data. Local variation in conditions and danger levels are likely to exist. To produce more accurate forecasts, we need information. Please send an email to [email protected]

Confidence

Poor - Due to limited field observations

Weather Forecast

Drier and colder conditions are forecast for Saturday. Strong easterly winds may occur in the bigger valleys as cold air flows out to the sea. The next storm is expected to hit the north coast as early as Sunday noon. Expect strong winds and heavy precipitation Sunday night and Monday. The freezing levels should rise to near 1000 metres with the new storm.

Avalanche Summary

I suspect there was a decent natural cycle during the storms earlier this week, especially on wind-loaded slopes. The possibility of human-triggered wind and storm slab avalanches is expected to remain for the forecast period.

Snowpack Summary

Another 10-15cm adds to the recent storm snow totals. Varying temperature, precipitation intensity, and wind throughout the recent storms have probably resulted in weaknesses strewn throughout the top metre or so. However, the relatively warm post-storm temperatures on Thursday should favor settlement and strengthening. The mid and lower snowpack is generally well settled and strong, with an old rain crust near the ground. Strong outflow winds from the east may build new wind-slabs on westerly aspects in areas that have snow available for transport.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.

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.