Avalanche Forecast

Issued: Mar 16th, 2017 4:52PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Storm Slabs, Deep Persistent Slabs and Loose Wet.

Ruari Macfarlane, Parks Canada

Waterton Lakes.

Avoid traveling below slopes overhung by cornices. Pay attention to precipitation amounts and freezing levels on Saturday - danger will vary accordingly. Avoid traveling through avalanche runout zones during periods of heavy loading.

Summary

Weather Forecast

Friday: Clear, becoming cloudy. Light-Moderate SW wind. Freezing level 500m, rising to 1800m. Treeline Low-8, High -2.5Saturday: Rain/Snow, heavy in the West. Freezing Level 2450m. Extreme SW winds.Sunday: Clearing. Strong SW winds, easing. Freezing level 1000m. Treeline Low -10, High -9

Snowpack Summary

Rain (upto 45mm) on Tuesday and Thursday turned the snowpack moist at Treeline and Below. A surface freeze temporarily increases stability for Friday. Strong SW winds are building slab and cornices higher up. All the recent snow and warmth has deep Persistent weak layers hovering around tipping point in isolated features.

Avalanche Summary

On Thursday a size 2.5 Deep Persistent slab was observed from a cross-loaded, typically rocky slope in the Alpine. This failed near ground on a NW aspect at 2200m. Two other Deep Persistent slabs (Size 3) were observed during the past week, running from the Alpine to Valley bottom. Numerous Large, Loose Wet avalanches were observed on Wednesday.

Confidence

Intensity of incoming weather systems is uncertain on Saturday

Problems

Storm Slabs

New snowfall with SW wind & warm temps will create fresh, reactive storm slabs on lee slopes. Expect these avalanches to be largest near the divide, including Cameron Lake area. Heavy snowfall is possible in Western areas on Saturday.

Avoid lee and cross-loaded terrain near ridge crests.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Deep Persistent Slabs

Significant ongoing snowfall accumulations, combined with sustained warm temperatures are currently stressing facets in the lower snowpack, and a crust in the mid snowpack.

Avoid thin, rocky or sparsely-treed slopes.Minimize exposure to overhead avalanche terrain, large avalanches are reaching run out zones.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 4

Loose Wet

Rain to Treeline on Saturday will destabilize the snowpack. If the snow feels wet and punchy, avoid steep slopes. Isolated Wet Slab avalanches are also expected through the weekend. These are harder to predict.

Avoid terrain traps, such as gullies, where the consequences of a small avalanche could be serious.Use extra caution on solar slopes, or if the snow is moist or wet.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Mar 19th, 2017 4:00PM