Avalanche Forecast

Archived

Jan 9th, 2014–Jan 10th, 2014

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Regions

Purcells.

Complex avalanche conditions at the moment. The answer to this type of avalanche problem lies in conservative terrain selection. Visit the blog for thoughts on the recent pattern of accidents in the Purcells.

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain on Saturday

Weather Forecast

A westerly flow dominates the next few days. A number of weather systems are lined up to bring varying amounts of precipitation and wind to the interior regions.Friday: Light snowfall, alpine temperatures -10, winds moderate to strong west and southwestSaturday: Moderate snowfall, alpine temperatures -8, winds strong to extreme west and southwest. Freezing levels possibly rising to 1200m in the morning.Sunday: Moderate snowfall, Alpine temperatures -8, moderate west winds.

Avalanche Summary

There have been a few different close calls with large avalanches in the north of this region in the last three weeks. Check out the incident database for more details. There have been no recent reports of avalanche activity. However I would expect to see an increase in natural and rider/skier triggered avalanches as new snow amounts continue to accumulate and the wind speeds pick up over the next 2-3 days.

Snowpack Summary

Up to 10 cm of new snow sits on a variety of snow surfaces ranging from stiff wind slab, a soft layer of facetted snow and/or surface hoar. These sit on top of old wind slabs and a couple of persistent weak layers that exist in the upper meter of the relatively thin snowpack. The mid December surface hoar is buried around 30-90 cm. The early December facet/crust combo is buried down 50-150 cm. Both interfaces give variable results with snowpack tests, but professional operators are treating them with caution.A bigger concern, especially in the Northern part of the region is a layer of weak sugary depth hoar crystals at the base of the snowpack that lie above a crust from early October. Several large avalanches in the last two weeks have been attributed to failures at this layer. Wide propagations on relatively gentle terrain have been noted, as well as a tendency for seemingly disconnected slopes to become connected by one large avalanche.

Problems

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.