Avalanche Forecast

Issued: Jan 21st, 2013 4:00PM

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

garth lemke, Parks Canada

Jasper.

If freezing levels and solar input increases dramatically on Tuesday, the potential to trigger an avalanche will increase in the afternoon. Overnight temperatures and overcast conditions seem to be regulating this effect somewhat.

Summary

Weather Forecast

Tuesday will be cloudy periods, slightly warm temperatures with freezing level to 1600m and strong W winds at 3000m. Wednesday will have cooling trend, 5mm of precip, and moderate-strong treeline and alpine West winds. Thursday will warm slightly but little change expected.

Snowpack Summary

Last week's extreme NW winds stripped fetch zones. Hard slabs are present on all lee slopes tree line and above. Surface hoar is found 10-40cm down depending on wind-loading patterns. Weak basal facets dominates thin areas. Below tree line, the old storm snow is over a rotten facet base. Colder overnight temperatures helping stability.

Avalanche Summary

A few natural size 1.5-2 avalanches noted Monday on steep unskiable SW alpine terrain but overall activity has subsided. Previous to Saturday, numerous full depth natural slab avalanches occurred on thin, steep, lee alpine slopes up to size 3. They ran far in paths with steep run outs.

Confidence

Freezing levels are uncertain on Tuesday

Problems

Wind Slabs

Last week's extreme winds have developed hard wind slabs on lee aspects. It sporadically overlies a buried surface hoar from Jan 6th. Avalanches were initially observed on thin, steep, lee slopes in the alpine but activity subsided since Friday.

Be careful with wind loaded pockets while approaching and climbing ice routes.Be aware of the potential for wide propagations due to the presence of hard windslabs.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Deep Persistent Slabs

Initiating the surface wind slab can trigger this deeper weakness. This situation will more likely occur in shallow snowpack areas. Less activity since Friday due to cooler temperatures but expect human triggering remains possible on steep slopes.

Be aware of thin areas that may propogate to deeper instabilites.Carefully evaluate big terrain features by digging and testing on adjacent, safe slopes.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Jan 22nd, 2013 4:00PM