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Avalanche Forecast

Archived

Jan 9th, 2012–Jan 10th, 2012

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

Regions

Northwest Inland.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain on Thursday

Weather Forecast

A few more cm of new snow is expected on Monday night for Coastal and Interior regions. Temperatures are expected to drop to about -15 in the alpine by Tuesday morning as a ridge of high pressure moves into the region. Wednesday is expected to be mostly clear, but not as cold as Tuesday. The next system should be on the coast by Wednesday night or Thursday morning.

Avalanche Summary

Reports of natural avalanches up to size 2.5 from northerly aspects. I suspect windslab releases from snow transported by the recent storm.

Snowpack Summary

Heavy rain up to about 1000 metres on Saturday night ended around 0800 Sunday. Cooling since the storm has created a rain crust up to about 1200 metres. There is about 235 cm at 1500 metres. There is an old rain crust that is buried down about a metre that is knife hard and showing old facets above and below. The snowpack is well settled below the rain crust down to the ground. The snowpack in the alpine is highly variable. Strong winds with almost every storm this winter have scoured ridges and knolls down to bare ground, and exposed boulders on some slopes.

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.

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.