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Avalanche Forecast

Archived

Jan 10th, 2017–Jan 13th, 2017

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

Regions

Waterton Lakes.

Low density new snowfall is producing natural Storm Slab and Loose Dry avalanches. Winds are forecast to pick up either Wednesday or Thursday - as soon as it does, expect the primary problem to become Wind Slab, and avalanche size to increase.

Weather Forecast

Expect sun and no precipitation to predominate the foreseeable future. Temperatures are beginning a rising trend, with a strong inversion possible Thursday-Friday. By Friday, expect highs between -5 and -10. Winds for Wednesday are uncertain, but expect Moderate or Strong SW winds on Thursday to redistribute recent snowfall. Wind easing Friday.

Snowpack Summary

30cm of low density new snow is sluffing readily in sheltered areas, and has formed touchy storm slabs on many wind exposed slopes at Treeline and above. Expect any winds to easily pick up the new snow, quickly forming windslabs on lee slopes. In the middle of the snowpack is a layer of facets that is still producing occasional sudden shears.

Avalanche Summary

On Monday and Tuesday, several small (Size 1 - 1.5) natural Storm Slab and Loose Dry avalanches were observed in alpine and open treeline terrain.On Tuesday, forecasters ski cut a Size 1 Storm Slab at Treeline, and a few Size 1 - 1.5 Loose Dry avalanches in steep terrain at and below treeline. These were easily triggered & gained mass quickly.

Confidence

Wind speed and direction is uncertain on Wednesday

Problems

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.

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.