Avalanche Forecast

Issued: Dec 4th, 2014 8:14AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Persistent Slabs.

ghelgeson, Avalanche Canada

Kootenay Boundary.

Riding north of Nelson? Take a look at the South Columbia forecast. Please email your observations to forecaster@avalanche.ca

Summary

Confidence

Poor - Due to the number of field observations

Weather Forecast

Synopsis:Â A pattern shift is underway as dry and cold northwest flow gives way to rather mild southwest flow.Â 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:Â 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; Â 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

Pay attention to how the snow feels as you travel, as there may be the odd old wind slab hiding out in wind exposed terrain. Watch for the formation of fresh, shallow yet sensitive wind slabs late Friday.

Dig down to find and test weak layers before committing to a line.>Be cautious as you transition into wind affected terrain.>Be prepared to modify your plans to match changing conditions.>

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Persistent Slabs

Limited to the northern half of the forecast area, the persistent slab problem has the potential to ruin your winter before it starts. Avalanches initiating high in the snowpack may step down resulting in a surprisingly large avalanche.

Avoid shallow snowpack areas where triggering is more likely.>Be aware of thin areas that may propogate to deeper instabilites.>Be aware of the potential for large, deep avalanches.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 5

Valid until: Dec 5th, 2014 2:00PM