Avalanche Forecast

Issued: Dec 9th, 2012 4:00PM

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

garth lemke, Parks Canada

Jasper.

Parkers Upper telemetry indicates since 8pm Saturday, winds blowing steady SW 20-60km/hr gusting 90. Other stations also increasing wind values. Prime windloading conditions. Expect changing conditions and increased likelihood for natural activity.

Summary

Weather Forecast

Jet stream lies over BC bringing strong NW alpine winds for next couple of days. 2 systems will bring continuous yet light snow with potentially more amounts in the Icefields. A snow warning exists just to the West which may trickle into the Icefields area. Milder temperatures are expected next couple of days and reduced winds by Tuesday.

Snowpack Summary

Moderate gusting strong swirling alpine winds are transporting the available 20cm or more of surface snow. Expect variable loading patterns with local terrain influences. Saturday's snow pit above Parkers Slabs was 190cm thick on a well settled mid pack. Whatever was on the surface is likely getting redeposited. Still overall variable snow depths.

Avalanche Summary

Saturday three size 2-2.5 avalanches were noted now 48-72 hours old, 40 degree plus, NW aspect, cross loaded gullies. Thursday' s explosive work on parkers slabs with 22 avalauncher rounds produced one size 2 slab avalanche in a wind loaded location on smooth steep rock slab. Patrol South today had limited visibility but swirling winds encountered.

Confidence

Wind effect is extremely variable

Problems

Wind Slabs

Increasing winds are creating windslabs on mainly, but not exclusively, lee aspects particularly at high elevation ridge tops and specific features such as alpine gullies. Watch for reverse loading patterns and increasing natural activity.

Avoid travelling in areas that have been reverse loaded by winds.Avoid lee and cross-loaded terrain near ridge crests.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Persistent Slabs

A persistent facetted weakness can be found around a mid-pack crust.

Avoid unsupported slopes.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Deep Persistent Slabs

This layer continues to develop in shallow snowpack areas which would be your likely trigger spots. Has potential to scrub to ground if initiated.

Avoid shallow snowpack areas where triggering is more likely.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Valid until: Dec 10th, 2012 4:00PM