Avalanche Forecast

Archived

Feb 18th, 2012–Feb 19th, 2012

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Purcells.

Confidence

Good

Weather Forecast

We're entering a more active pattern which should persist through the middle of next week.Sun: A ridge of high pressure rebuilds during the day allowing temperatures to cool slightly while winds ease and switch from the SW to NW. A bit of instability from Saturday's storm will produce the odd flurry, but skies should clear in the afternoon. Look for 1500m temps to climb to -2 during the day.Mon/Tue: A few weak systems pass over the region favoring west slopes. Nothing in the flow is particularly well organized, it's the kind of setup that has the potential to bring 2-4 cm a day. Precip totals will be quite variable throughout the region, favoring the west slopes. 1500 m temps: High -3, Low -7

Avalanche Summary

No new avalanche activity reported Thursday or Friday.

Snowpack Summary

Widespread surface hoar has been buried by 5 - 10 cm of new snow in most of the region. The exception is terrain closer to the bugs where the interface is down 20-40cm. A melt-freeze crust has developed on southerly aspects at all elevations. North and east aspects continue to have dry snow and some surface sloughing in steep terrain. Basal facets have not been reactive, but operators continue to monitor this layer in tests. Triggering this deep persistent weak layer is unlikely, but shallow snowpack areas or shallow weak areas adjacent to deeper wind loaded slopes are suspect locations.

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.

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.