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Avalanche Forecast

Archived

Nov 22nd, 2015–Nov 23rd, 2015

Alpine
Below Threshold.
Treeline
Below Threshold.
Below Treeline
Below Threshold.
Alpine
Below Threshold.
Treeline
Below Threshold.
Below Treeline
Below Threshold.
Alpine
Below Threshold.
Treeline
Below Threshold.
Below Treeline
Below Threshold.

Regions

Purcells.

This bulletin is based on limited observations. Conditions vary greatly across the region so take the time to gather information about the snowpack as you travel. We always appreciate any observations from your day submitted to the MIN.

Confidence

Fair - Due to the number and quality of field observations

Weather Forecast

A cold front descending from the North is going to bring between 5 and 20 cm of snow over the next couple of days. The greatest snowfall accumulations are expected for the Dogtooth Mountains around Golden. By Wednesday a high pressure system will settle over BC bringing several days of chilly but stable weather.

Avalanche Summary

I'm working with limited observations but there weren't any reports of new avalanche activity over the weekend. However, given the presence of wind slabs and a lingering basal weakness on north to east facing terrain in the alpine I am concerned that smaller wind slab avalanches could possibly step down to deeper layers.

Snowpack Summary

The forecast snow will fall on a variety of old surfaces. In the north of the region, folks were finding low density powder snow, deep trail breaking and great riding conditions over the weekend. Here the new snow will hide pockets of fresh wind slab on east and northeast aspects. Further south, around Kimberly, reports on the Mountain Information network suggest that a surface crust can be found up to 2200m. Below this we're dealing with a complex snowpack. A couple of layers of surface hoar formed earlier in the month. Where they exist, they are likely to be found down 50 to 100 cm below the surface. Depending on where you dig, you could also find one, or more crusts. It would be wise to test these layers before committing to a slope. Facets may exist just above the ground on shaded slopes in the alpine. Remember that it's still a young snowpack. Rocks and stumps may be lurking unseen just below the surface. Ride with care!

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.