Avalanche Forecast

Issued: Feb 18th, 2017 4:17PM

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

Ruari Macfarlane, Parks Canada

Waterton Lakes.

You can brave breakable crust down low, to access reasonable conditions at Treeline. Alternatively, you might choose to hone your skills in the new Avalanche Transceiver practice area, on the right just before the Little Prairie trailhead.

Summary

Weather Forecast

Sunday: Snowfall (5-10cm) ending early, some sun may poke through in the afternoon. Moderate SW wind, increasing. Freezing level 1500m.Monday: Becoming cloudy, scattered flurries. Moderate SW winds. Freezing level 1400m.Tuesday: New snowfall ( 5 - 15 cm forecast). SW winds becoming Strong-Extreme. Freezing Level 1600m.

Snowpack Summary

New snow/wind fuels Wind Slab development, over breakable crust below 1900m (but to the alpine on solar aspects). A older, cohesive slab below has produced Moderate, Sudden test results on a Persistent Weak Layer (PWL) down 60-90cm (crust on sunny slopes, facets in sheltered areas between 1700-2150m, basal facets in shallow snowpack areas.)

Avalanche Summary

On Friday a few Small - Large (Size 1 - 2) Storm Slab and Loose Wet avalanches were observed, mostly near the divide. On Thursday, Several Small - Large avalanches were observed in steep paths Below Treeline. They were mainly Loose Wet, triggered by rain. One was a Deep Persistent Slab, releasing on ground in a thin snowpack area.

Confidence

Due to the number of field observations

Problems

Persistent Slabs

A 70cm slab of previous storm snow sits on a crust below 2000m, and/or facets. These are widespread, but hard to trigger. Dig in safe areas on adjacent slopes, do snowpack tests and gain more information, before entering into consequential terrain.

Ride slopes one at a time and spot your partners from safe locations.Pay attention to overhead hazards like cornices which could easily trigger persistent slabs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Wind Slabs

Use caution in lee areas. New snowfall mixed with wind loading is creating Wind Slabs.Use caution above cliffs and terrain traps where small avalanches may have severe consequences.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Deep Persistent Slabs

Several large avalanches have been observed in the front ranges and/or windward terrain, where storm snow fell on shallow facets over ground. Rain on Thursday triggered an avalanche on the basal facets, in a shallow snowpack area Below Treeline.

If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.Avoid thin, rocky or sparsely-treed slopes.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely

Expected Size

2 - 4

Valid until: Feb 21st, 2017 4:00PM