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Avalanche Forecast

Archived

Jan 20th, 2017–Jan 23rd, 2017

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

Regions

Waterton Lakes.

Ski conditions are very poor below 1900m, and reasonable above.  Treat big open slopes at Treeline elevations the same as you would in the Alpine - the current problem lurks in big features with areas of variable snowpack depths. 

Weather Forecast

A stationary Low equals Status Quo.  Temperatures have cooled since midweek, and will fluctuate with daytime warming between -13 and -3 . Light winds and a mix of sun and cloud will dominate the forecast period, other than overcast skies late Saturday. A light Upslope event with overcast skies and flurries may arrive late Sunday or Monday.

Snowpack Summary

A few Cm of recent snowfall is well bonded to harder, wind affected snow below. A thin, breakable rain crust on the surface extends up to 1900m, with Moist snow below. Faceted layers in the mid and lower snowpack remain a concern, particularly in shallow snowpack areas where facetting is more pronounced and triggering is more likely.

Avalanche Summary

A few small avalanches Size 1 were noted from extreme terrain Below Treeline on Thursday and Friday. No large avalanches have been observed since a natural Deep Persistent Slab avalanche a week ago. This initiated in a shallow area in a wind-affected Alpine basin, when a small windslab from above stepped down to a faceted crust near ground.

Confidence

Due to the number of field observations

Problems

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.