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Avalanche Forecast

Archived

Feb 10th, 2013–Feb 11th, 2013

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.
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.

Confidence

Good

Weather Forecast

Synopsis: A series of frontal systems are expected to bring moderate precipition amounts to the region Monday and Tuesday, with a drying trend on Wednesday.Monday: Around 5cm new snow, maybe a little more for areas right next to the coast. Freezing level around 700m. Strong SW winds gusting to 70 km/h at ridgetop.Tuesday: 10-20cm new snow. Freezing level around 700m. Strong southwesterly winds gusting to 70 km/h at ridgetop.Wednesday: Dry, with a mix of sun and cloud. Freezing level at valley bottom. Light NW winds.

Avalanche Summary

Small avalanches (size 1) were human-triggered in wind slab deposits on Saturday.

Snowpack Summary

Recent weather has been relatively benign, with generally light snowfall adding 5-10cm at a time. Relatively light winds have accompanied these snowfall pulses with some stronger outflow winds closer to the coast. At elevations below 1300 m you might find a crust close to the surface from recent warm temperatures and/or rain.In the upper snowpack, various melt-freeze crusts remain a concern. Depending on your location, you may encounter crusts as shallow as 40cm and as deep as 110cm. Recent compression tests show both resistent and sudden planar results and an extended column test indicated a propensity for propagation if the layer was triggered. It is certainly worth keeping these layers on your radar in regards to distribution and reactivity in the areas that you are riding. The mid and lower snowpack layers are generally well settled..

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.