Avalanche Forecast

Issued: Jan 24th, 2016 4:58PM

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

Ruari Macfarlane, Parks Canada

Waterton Lakes.

While Wind Slab predominates , uncertainty exists about the sensitivity of buried weak layers - a cautious approach is recommended at Alpine and Treeline elevations.

Summary

Weather Forecast

A mix of sun and cloud with isolated flurries daily. Freezing levels will hover around valley floor, rising slightly higher by Wednesday. Ridge winds are forecast at Moderate from the W-SW, rising to strong by Wednesday.

Snowpack Summary

15cm of new fluff sits on Fridays' Rain Crust below 2100m, and on thick, dense Wind Slabs above this. Forecast wind will build new wind slabs in lees. The primary concern, though, are old Wind Slabs. These may propagate widely, especially if they initiate on/step down to a weak layer buried 40-80cm: Crust on solar aspects, Surface Hoar on shady.

Avalanche Summary

Two large Slab avalanches were observed today on lee N-E aspects, initiating around 2300m. These are likely Wind Slabs, but could be on the Jan 4 Surface Hoar. Earlier, a widespread natural cycle of small avalanches was observed during Fridays warm storm, with a few isolated large avalanches. One of these was a persistent slab on the Jan 4 crust.

Confidence

Due to the number and quality of field observations on Sunday

Problems

Wind Slabs

Buried Wind Slabs are widespread in exposed areas, and are largest in the SW of the Park. These are hidden under recent snow, and touchier new Wind Slabs. Use extra caution on lee slopes - clues include cornices up above, and a deep snowpack.

Avoid steep lee and cross-loaded slopesIf triggered the wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

A weak layer that was buried in early January was showing signs of strengthening before Fridays' storm, but has not been ruled out as the potential failure plane of several large, recent slab avalanches. Consider avalanche consequence at all times.

Carefully evaluate terrain features by digging and testing on adjacent, safe slopes.Assess start zones carefully and use safe travel techniques.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Valid until: Jan 27th, 2016 4:00PM