Avalanche Forecast

Issued: Mar 21st, 2017 5:53PM

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

Ruari Macfarlane, Parks Canada

Waterton Lakes.

A strong crust is allowing fast travel Below Treeline - for those trained and equipped for avalanche terrain, it's a good time to cover ground, and discover new areas of the Park. Be wary of exposure to cornices, and large Alpine slopes.

Summary

Weather Forecast

Wednesday: Cloudy, Light precipitation ending in the morning. Rain/snow line at Treeline, lowering. Ridge Winds: SW, becoming Strong. Freezing level: 1950m. Treeline High 0.Thursday: Sun & cloud. Ridge winds: Moderate SW. Freezing Level: 1000m, rising to 1500m. Treeline High -5Friday: Cloudy, flurries later. Moderate SW winds. Freezing Level 1900.

Snowpack Summary

A thick crust Below Treeline overlies a Moist snowpack. The crust thins out at lower treeline elevations, with a dry, late winter snowpack in the Alpine. New snow instabilities from Saturdays's storm are settling. A crust from Mid Feb, down 1m, is giving some sudden results in tests. The bottom of the snowpack is faceted, and still weak in places.

Avalanche Summary

No new avalanches observed on Tuesday. On Saturday, a warm storm caused a widespread cycle of Large (Size 2-3) Natural avalanches, mainly in the West where precipitation was heaviest. Many Wet Slabs initiated around 1900-2200m, some on the February 16 MFcr. Several Storm slabs & Deep Persistent slabs failed in steep, lee Alpine terrain.

Confidence

Due to the number of field observations

Problems

Storm Slabs

These still exist in steep Alpine terrain, on lee aspects away from the wind, where warm heavy snow on Saturday fell on colder snow below. These are largest along the borders of Montana and BC (blame them!), as snowfall was heaviest in the West.

Avoid lee slopes with any steepness over 40 degrees.Carefully evaluate terrain features by digging and testing on adjacent, safe slopes.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 3

Deep Persistent Slabs

A crust down 1m (to Treeline, and higher on solar aspects) and Facets in the bottom 1/3rd of the snowpack, are slowly adjusting to recent heavy loading. Human triggering of large, destructive avalanches remains Possible, in the wrong terrain.

Avoid thin, rocky or sparsely-treed slopes.Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 4

Valid until: Mar 24th, 2017 4:00PM