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Avalanche Forecast

Archived

Feb 21st, 2021–Feb 24th, 2021

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
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.

If you decide to brave the blizzard, avoid avalanche terrain. Warming, wind, and new snow are forming slabs over a layer of weak facets. These will be reactive in unusual places at lower elevations including in the burnt forest.

Weather Forecast

Sunday night through Monday will bring blizzard conditions with strong to extreme westerly winds and anywhere from 20-40cm of new snow. Models vary on freeing levels which could peak anywhere from 1400 to 1800m Monday night. Tuesday and Wednesday will see progressively cooler conditions and clearing skies with wind continuing out of the west.

Snowpack Summary

Extreme southwest through westerly winds continue to build wind slabs over a weak facet layer on top of older facetted snow. In lower elevations, this sits on a hard crust increasing the potential for wide propagations. Midpack is made up of facets and decomposing crusts of varying resistance. Thin snowpack areas are very facetted.

Avalanche Summary

A natural Size 2 avalanche with a 40cm crown was seen on a crossloaded west aspect well below ridgetop at 1900m triggered by extreme winds on Sunday. It likely failed on a layer of facets. Visibility was poor, but forecasters suspect several other similar failures in the forecast region.

Confidence

Freezing levels are uncertain on Monday

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.