Avalanche Forecast

Archived

Dec 12th, 2015–Dec 13th, 2015

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 unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Northwest Inland.

This bulletin was produced using very few field observations. If you've been out in the mountains, please share your observations on our Mountain Information Network.

Confidence

Low - Due to the number of field observations

Weather Forecast

On Sunday, expect mainly cloudy skies and light northwest winds. By late Monday and Tuesday, the region could see up to 10cm of new snow and strong southwest winds. The freezing level should hover around valley bottom for the entire forecast period.

Avalanche Summary

No recent avalanches have been reported from the region.

Snowpack Summary

As much as 60cms of settled snow may now sit on a layer of buried surface hoar, although I'm unsure of the layer's reactivity and spatial distribution. I'd dig down and test for this potentially weak layer before committing to any steep lines, especially on sheltered north facing slopes at tree-line and just below. Recently formed wind slabs are reported to exist at alpine elevations.Lower below tree-line elevations may still be below threshold for avalanches.

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.