Avalanche Forecast

Issued: Jan 10th, 2017 4:33PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs, Wind Slabs and Persistent Slabs.

Ruari Macfarlane, Parks Canada

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.

Summary

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

New storm snow with a little wind has created touchy Storm Slabs on many treeline and alpine slopes, especially likely in wind-exposed areas. This will change to a Wind Slab problem (see below) as soon as winds are visibly transporting snow.

Be cautious of sluffing in steep terrain.If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Wind Slabs

This problem will replace the Storm Slab problem as soon as winds arrive. Rising temperatures will accelerate slab development. Monitor winds closely, watch for signs of wind affect, and avoid lee slopes if snow is blowing.

Use caution in lee areas. Wind loading will create slabs.Watch for shooting cracks or stiffer feeling snow. Avoid areas that appear wind loaded.

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 3

Persistent Slabs

A weak layer of facets in the middle of the snowpack will be trying to adjust to new loading from recent snowfall, and forecast wind transport. A Moderate, Sudden Planar result in a snowpack test on Tuesday indicates potential for human triggering.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Jan 13th, 2017 4:00PM