Avalanche Forecast

Issued: Feb 15th, 2017 4:26PM

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

Ruari Macfarlane, Parks Canada

Waterton Lakes.

Light precipitation on Thursday may not be enough to salvage the ski quality, but you can hone your skills in the new avalanche transciever practice area, across the road from the Little Praire trailhead!

Summary

Weather Forecast

The Jet Stream passes overhead, generating strong warm winds from the SW. The flow slackens/cools during Friday.Thursday: Light snowfall (5 - 25cm), except rain below 1800m, Strong SW winds, Freezing Level 2000m, surface refreeze expected at upper elevations.. Friday/Saturday: -3 to -8, Flurries, Moderate SW winds backing to Light Easterlies.

Snowpack Summary

Freezing Levels above mountaintop for 48 hours combined with sun have consolidated the upper snowpack, especially on solar aspects. A thick, cohesive storm slab is producing Moderate/Sudden test results on a Persistent Weak Layer down 40-80cm (crust on sunny slopes, facets in sheltered areas from 1700-2150m, basal facets in shallow snowpack areas.)

Avalanche Summary

On Tuesday, several small Loose Wet avalanches were observed in steep Alpine terrain. One of these triggered a small (Size 1.5) Storm Slab in extreme terrain. On Wednesday, widespread snowballing was noted.

Confidence

Forecast snowfall amounts are uncertain on Thursday

Problems

Storm Slabs

While deep Storm Slabs from last weeks heavy snowfall have gained strength, they sit over a facet-crust combo on solar slopes below 2100m, and over facets (slowly strengthening) in sheltered/treed areas. If triggered, these may be destructive.

Dig down to find and test weak layers before committing to a line.Ride slopes one at a time and spot your partners from safe locations.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Wind Slabs

New snowfall accompanied by Strong SW wind on Thursday through Friday morning could build fresh wind slabs on lee slopes, 15-40cm thick, & more likely to be reactive where they sit over a sun/temperature crust - most likely East & South-East aspects.

Use caution in lee areas. Wind loading could create slabs.Plan escape routes and identify safe zones before committing to your line.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Deep Persistent Slabs

Several large avalanches were observed last week, all in the front ranges and/or in windward terrain, where storm snow fell on large facets in a shallow snowpack.

Carefully evaluate terrain features by digging and testing on adjacent, safe slopes. If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely

Expected Size

3 - 4

Valid until: Feb 18th, 2017 4:00PM