Avalanche Forecast

Issued: Jan 15th, 2013 7:37AM

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.

tim haggarty, Parks Canada

Waterton Lakes.

Watch for inversion conditions over the next few days. Remember that slopes above you may be warmer than what you can feel. Warming could make the persistent slab problem reactive. Be wary of sheltered locations that may hold buried surface hoar.

Summary

Weather Forecast

Warm air is expected to move in above the current cold air early Tuesday. The resulting inversion conditions may bring temperatures above freezing at upper elevations. When combined with solar radiation if the skys are clear, this could have a radical effect on the snowpack with windslabs and some lurking persistent slab problems.

Snowpack Summary

Up to 5cm HN with Strong NW winds creating windslabs near exposed ridge crests. 30-40cm low denisty snow is sitting on a 20-40 cm slab over the Jan 5 interface. Moderate Sudden Planar test results can be found on preserved surface hoar at this interface in isolated, sheltered locations. There is a high degree of variability with this layer.

Avalanche Summary

A few surface windslabs have been observed in the past 3 days sizes 2 to 2.5. These have been in steep terrain near ridge crests or below extreme terrain. Cornice failures, wind loading, and sluffs have served as the triggers. No activity has been seen on the Jan 5 persistent slab: its spotty nature and the cold snow have kept things quiet for now.

Confidence

Freezing levels are uncertain

Problems

Wind Slabs

W and NW winds have been creating slabs near ridge lines over the past few days. A few natural avalanches have been seen that are 10-30cm deep. Feel for changes in the upper snow pack as you enter open areas. A small slab may trigger a deeper one.

Be careful with wind loaded pockets while approaching and climbing ice routes.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

Jan 5 interface in sheltered locations where preserved surface hoar can be found down 50 to 90 cm. Dig down often to identify this layer and avoid steep or unsupported slopes where surface hoar is present. Triggering this layer would be serious.

Dig down to find and test weak layers before committing to a line.Choose conservative lines and watch for clues of instability.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Valid until: Jan 18th, 2013 4:00PM