Avalanche Forecast

Issued: Jan 1st, 2015 4:00PM

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

jon stuart-smith, Parks Canada

Waterton Lakes.

NW winds have redistributed snow from recent storms, building slabs in a slightly unusual pattern. Now almost 1m of snow at higher elevations on top of weak December layer of facets and in places surface hoar but still willows showing below 1800m.

Summary

Weather Forecast

Clear but continued NW winds until Saturday morning when another cold front arrives. Temperatures will drop again and we could see 10-15cm of snow at higher elevations. Winds will switch back to the normal SW following the passage of the front.

Snowpack Summary

The slab over the persistent weak layer consisting of surface hoar and facets over a strong crust is now 80 to 100cm thick at up ridgetop but only 40cm below treeline. Strong west and northwest winds have create slabs, some in slightly unusual locations because of the northerly component of the winds.

Avalanche Summary

The new snow is hiding any evidence of recent avalanche activity however at least three large avalanches occurred during the last storm. Natural avalanche activity seems to have tapper off for no but could increase with new snow forecast for Sunday.

Confidence

Intensity of incoming weather systems is uncertain on Sunday

Problems

Persistent Slabs

The weak snow above the crust is now primed with a big enough slab for there to be serious consequences. In the alpine this problem will likely be limited to N and E aspects but at treeline it is widespread. Use extra care in open, sheltered terrain.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Dig down to find and test weak layers before committing to a line.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 3

Wind Slabs

NW ridgetop winds over the last couple of days have built slabs, some in unusual locations for our area. At lower elevations and closer to the prairies, the winds have been more in a SW direction making the problem more complex.

Use caution in lee areas. Recent wind loading have created wind slabs.If 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 - 2

Valid until: Jan 4th, 2015 4:00PM