Avalanche Forecast

Issued: Mar 14th, 2017 5:10PM

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

Ruari Macfarlane, Parks Canada

Waterton Lakes.

In addition to listed Avalanche Problems, Cornices have also been very active recently. These will continue to grow. Some will fall. Bigger than your pickup truck, these are a perfect trigger for Very Large slab avalanches. Know what's above you.

Summary

Weather Forecast

Wednesday: Cloudy. Light snowfall (rain below 2100m). Extreme SW wind, easing. Freezing level 2300m. Treeline High 2, Low -1.5Thursday: Snowfall overnight (10-15cm), except rain Below Treeline, easing. Moderate-Strong SW wind. Freezing Level falling to 1500m. Friday: Sunny. Moderate West wind. Freezing level 800m, rising. Treeline Low-8, High -2.5

Snowpack Summary

Warm temperatures have helped Storm slabs bond & settle, but rain to Treeline on Tuesday/Wednesday adds free water to the upper snowpack, while Strong SW winds build slab and cornice higher up. Persistent weak layers in the mid and lower snowpack appear to be waking up, with warmth adding to the stress of near-daily snowfall since February 25.

Avalanche Summary

On Tuesday a Large (Size 3) slab avalanche, up to 2m deep, was observed on a N aspect at 2200m. It ran to valley floor. Several small Loose Wet avalanches were observed in steep terrain Below Treeline. On Sunday, another Size 3 Deep Persistent slab avalanche occurred on a cross-loaded NW aspect, suspected to have failed on deeply buried facets.

Confidence

Forecast snowfall amounts are uncertain on Thursday

Problems

Storm Slabs

Old storm slabs were settling before Tuesdays precipitation, but increased load from further loading means it is worthwhile digging to test this slab. New snowfall with SW wind & warm temps will create fresh, reactive storm slabs on lee slopes.

Avoid lee and cross-loaded terrain near ridge crests.The new snow will require several days to settle and stabilize.

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

Elevations: Alpine, Treeline.

Likelihood

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 may reach run out zones.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 4

Loose Wet

Rain below 2100m on Tuesday and Wednesday will have a destabilizing effect on the snowpack. If the snow feels wet and punchy, avoid steep slopes.

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

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Mar 17th, 2017 4:00PM