Avalanche Forecast

Issued: Mar 3rd, 2017 4:00PM

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

Ruari Macfarlane, Parks Canada

Waterton Lakes.

We are seeing increased avalanche activity due to a potent combination of new snow, wind, warmth, and in some areas a tricky weak layer in the upper snowpack. On Saturday in particular, dangerous avalanche conditions exist. Be conservative.

Summary

Weather Forecast

Saturday: Steady snowfall Friday night easing to flurries (total 5-15cm expected). Ridgetop winds Extreme SW, easing to Moderate. Treeline Temps: High -4, Low -7.Sunday: Light snowfall. Ridgetop winds Light. Treeline Temps: High -8, Low -11.Monday: Light snowfall tapering off. Ridgetop winds Moderate SW. Alpine Temps High -9, Low -12

Snowpack Summary

Intense wind transport on Friday is creating Wind Slabs on lee slopes, over older wind slab layers. Down 50-80cm in some areas is a Persistent Weak Layer of small facets, 5-10cm thick. Where this layer exists (most likely on Sunny aspects at Treeline), the slab sitting on this layer is touchy. Storm slabs in sheltered areas are settling.

Avalanche Summary

On Thursday at Treeline, a small (Size 1) Persistent Slab was accidentally triggered by a skier, on a steep, South facing, cross-loaded slope, and a small natural Storm Slab was observed on a SE aspect. On Friday, several natural Small - Large (Size 1.5 - Size 2) Wind Slabs were observed. These were on N and E (lee) aspects, from 1950m to 2350m.

Confidence

Due to the number of field observations

Problems

Wind Slabs

Large volumes of snow are being blown around on Friday as this is written. Due to Extreme SW winds, the slabs this creates may be lower on the slope than you would usually expect. Don't be surprised! Transition carefully into any open terrain.

Watch for shooting cracks or stiffer feeling snow. Avoid areas that appear wind loaded.Avoid steep lee and cross-loaded features

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

In some locations, buried Wind Slabs sit unsteadily on 5-10cm of small facets. There is plenty of uncertainty about where these exist; however, they are most likely at Treeline, and are touchy on steep S and SW aspects where facets overlie a crust.

Carefully evaluate terrain features by digging and testing on adjacent, safe slopes. Choose conservative lines and watch for clues of instability.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Mar 6th, 2017 4:00PM