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Avalanche Forecast

Archived

Nov 20th, 2015–Nov 21st, 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, mainly from the north of the region. I would tread cautiously this weekend and take the time to gather snowpack information as I go. We always appreciate observations from your day submitted to the MIN

Confidence

Fair - Due to the number and quality of field observations

Weather Forecast

Freezing levels could rise as high as 1500m over the weekend with a temperature inversion developing overnight on Saturday. A cooling trend is expected with the arrival of the next storm system on Monday afternoon. Winds will be mainly light to moderate from the west throughout the forecast period.

Avalanche Summary

The storm earlier in the week resulted in a widespread avalanche cycle that produced some large avalanches. Last weekend there was a MIN report of rider a triggered avalanches on basal facets at treeline in the Dogtooth range near Golden.

Snowpack Summary

Up to 50cm of low density snow fell in the storm earlier this week. A MIN report from the south of the region suggest that some of this fell as rain forming a crust up to 1900m near Kimberley. Moderate westerly winds are likely to have formed pockets of windslab on east and northeast aspects.Below this we're 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 80 to 120 cm. Depending on where you dig, you might also find a couple of crusts. It would be wise to these layers before committing to a slope. Facets are likely to be found just above the ground at higher elevations in the Alpine.Remember that it's still a thin 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.