Avalanche Forecast

Archived

Nov 25th, 2015–Nov 26th, 2015

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

South Columbia.

Forecaster are working with very little information at this time. If you are riding in the back country, ride with caution, and perhaps dig a pit or two. Consider sharing your observations with others on the Mountain Information Network. MIN

Confidence

Fair - Due to the number and quality of field observations

Weather Forecast

Arctic air has moved in from the north bringing clear skies and cooler than average temperatures. Strong northerly winds at ridge top are expected to continue through Thursday afternoon, and then back off to more moderate speedsby Friday, after which winds should diminish to lighter values. Above freezing temperatures in the alpine are forecast to begin Friday morning and continue into the weekend, but valley bottoms will remain well below freezing.

Avalanche Summary

No recent report of avalanche activity in the forecast area, most likely owing to the fact that there are few professional members out in the back country at this time

Snowpack Summary

Monday's storm snow fell on a variety of old surfaces including crust, surface hoar and old settled snow. Arctic air moving into the region has resulted in northerly winds which may have formed small wind slabs on south facing features near ridge top. Warm temps and strong solar input formed a crust on south facing features which can be found underneath Monday's storm snow. There are at least three surface hoar layers in the snowpack buried on: Nov. 5th, Nov. 11th and Nov. 23rd. The first two have been largely unreactive. Facets may exist just above the ground on shaded slopes in the alpine.

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.