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Avalanche Forecast

Archived

Dec 4th, 2014–Dec 5th, 2014

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 unlikely, human triggered possible.
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.

Regions

Kootenay Boundary.

Riding north of Nelson? Take a look at the South Columbia forecast. Please email your observations to [email protected]

Confidence

Poor - Due to the number of field observations

Weather Forecast

Synopsis:  A pattern shift is underway as dry and cold northwest flow gives way to rather mild southwest flow.  Storm totals through the weekend look rather modest, but the door appears to be open to a succession of storms through the middle of next week.Friday: Freezing Level: 500m; Precipitation: 2-6mm | 2-8cm; Wind: Treeline: Light, SW | Ridgetop: Moderate, SWSaturday:  Freezing Level: 700m; Precipitation: 3-12mm | 4-15cm; Wind: Treeline: Moderate, SW | Ridgetop: Moderate/Strong, SW Sunday: Freezing Level: 1000m; Precipitation: 0-2mm | 1-3cm;  Wind: Treeline: Light, SW | Ridgetop: Moderate, SW

Avalanche Summary

No new avalanche activity to report.

Snowpack Summary

This forecast is based off a very limited data set. The snowpack north of Nelson is a different beast than the rest of the forecast region. If you're recreating north of Nelson, then current conditions more closely mirror those of the South Columbia. Check out that forecast to get a feel for the more complex snowpack and the associated Persistent Slab Problem. In the north it appears that two buried weak layers may be problematic: The mid November surface hoar/facet/crust combo down 70 - 90 cm and the weak sugary snow (large facets) near the ground. Little is known about the particulars of this setup, more observations would be great!In the southern portion of the region observations indicate that the snowpack is much more homogeneous and strong. There have been no reports of deeply buried weak layers. The Black Friday storm came in wet and finished cold. As a result, the structure consists of 15 - 25 cm of cold snow on top of a 2 - 6 cm supportive pencil/knife hard crust which was been observed as high as 2100. This crust could act as a bed surface in the future, but for now it appears to be bridging any deeper weaknesses.

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.