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Avalanche Forecast

Archived

Feb 12th, 2017–Feb 15th, 2017

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

Regions

Waterton Lakes.

The upper elevations may get there first dose of above freezing temperatures in a long time this week. Be extra cautious during the heat of the day.

Weather Forecast

A strong ridge of upper level high pressure will dominate the weather pattern for the next few days.Monday: Clear, Light SW ridge top winds, freezing level to 2500m (inversion possible)Tuesday: Clear, Light-Moderate SW ridge top winds, freezing level 3100m (inversion possible)Wednesday: Clear, Strong SW ridge top winds, freezing level to the moon.

Snowpack Summary

Strong to Extreme SW winds have built wind slabs low in lee areas. Prior to this wind, we received up to 150cm of fresh snow over the week (with freezing levels reaching 2000m near the end of the storm). This sits on a sun crust, wind crust or facets. Basal facets in shallow snowpack areas have been the cause of some large avalanches recently.

Avalanche Summary

No recent avalanche activity has been observed or reported. Thursday/Fridays warming and snow/rain event triggered a widespread natural avalanche cycle, many of these were large (Size 2 - 3). This included numerous avalanches from windward and front range locations that are typically wind-scoured scree, but are now holding snow.

Confidence

Due to the number of field observations

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.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.