Avalanche Forecast

Issued: Feb 19th, 2015 4:53PM

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

Tim Haggarty, Parks Canada

Waterton Lakes.

While travel at lower elevation remains difficult with poor coverage, it is still winter above 2000m and new, as well as old slabs remain available for human triggering. Cooler temperatures and a bit more snow should help freshen things up.

Summary

Weather Forecast

The Northerly flow is bringing cooler conditions for the weekend. Skies will become overcast late Thursday night and a welcome pulse of snow should arrive midday Friday from the prairies. By noon Saturday expect clearing and dropping temperatures as a NE flow continues to bring Arctic air into the mountains.

Snowpack Summary

Thin new windslabs now sit on the Feb 14 temperature crust that exists to 2300m and thin solar crusts to mountain top. Below this old windslabs cap the 50 to 80 cm slab that seems well bonded to the Jan 31 crust. The Mid-December layer that is down over 1m in most deep areas remains a concern in high shaded terrain presenting a shallow snowpack.

Avalanche Summary

Conditions have remained relatively cool with good overnight freezes. The February 14 crust has not been heated to the point of breaking down and is effectively limiting avalanche problems to minor surface concerns below 2000m and to ridge top on solar aspects. Elsewhere, concern for human triggering remains.

Confidence

Problems

Wind Slabs

Moderate ridge top winds mainly from the West have developed thin new slabs at treeline and above these will continue to develop with the addition of new snow on Friday.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Use caution in lee areas. Recent wind loading have created wind slabs.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

These old windslabs continue to produce reluctant shears 25 to 50 cm deep in the upper snowpack and are a concern above 2200m. Keep an eye on these if you are considering taking on serious terrain.

Carefully evaluate big terrain features by digging and testing on adjacent, safe slopes.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Deep Persistent Slabs

Now 40 to 120cm deep these slabs continue to stand out as a concern in the TL and ALP areas where there is not a strong Jan 31 crust over them (2200m+). Be particularly mindful in thin snowpack areas where this layer is more likely to be triggered.

Carefully evaluate and use caution around thin snowpack areas.Be aware of thin areas that may propogate to deeper instabilites.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Feb 22nd, 2015 4:00PM