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Avalanche Forecast

Archived

Nov 21st, 2015–Nov 22nd, 2015

Alpine
Natural avalanches possible, human triggered probable.
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.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

South Columbia.

Given the very limited information on hand for this bulletin, I would tread cautiously this weekend and take the time to gather snowpack information as I go. As always, we would love for you to submit any observations from your day to the MIN

Confidence

Good - Due to the number and quality of field observations

Weather Forecast

High pressure will persist over the region through Sunday before an advancing cold front the North brings moderate snowfall Monday and Tuesday. Sunday: Mainly clear, freezing levels rising up to 1100m with a temperature inversion extending to 2000m, light precipitation starting late in the day. Monday: 5 to15 cm of snow, southwesterly wind, a high of -10C in the alpine. Tuesday: 5 to 10 cm of snow, northerly wind, a high of -15C in the alpine.

Avalanche Summary

I'm working with limited observations but there haven't been any reports of avalanche activity. However, the avalanche cycle that occurred during and immediately after the storm earlier in the week produced some large deep avalanches.

Snowpack Summary

Up to 50cm of low density snow fell in the storm earlier this week. Over the last couple of days moderate westerly winds are likely to have moved this around and formed pockets of wind slab on east and northeast aspects. Below this were dealing with a complex snowpack. A couple of layers of surface hoar were formed earlier in the month. Where they exist, they are likely to be found buried down 65 to 120 cm. Depending on where you dig, you might also find one or more crusts. It would be wise to test these layers before committing to a slope. Facets can be found at the bottom of the snowpack at higher elevations in the alpine, especially on northerly aspects. Remember that its 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.