Avalanche Forecast

Issued: Jan 3rd, 2012 8:52AM

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

Avalanche Canada jfloyer, Avalanche Canada

Summary

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

A warm front passes over this region late today (Tuesday) bringing light or locally moderate precipitation--say 10 to 15 cm between Tuesday evening and midday on Wednesday. Freezing levels will rise to approximately 1800 m during this time and strong southwesterly winds are expected. On Wednesday evening, a cold front will pass, bringing another similar pulse of snow (10-15 cm between Wednesday evening and Thursday morning) and freezing levels down to surface levels. Late Thursday and into Friday a ridge of high pressure develops, keeping things cold and mostly dry. Winds should ease to light by Friday afternoon.

Avalanche Summary

A size 2 human-triggered avalanche occurred on Monday on a northwest aspect at 1700 m. The avalanche was triggered in wind slab; the fracture line was 30 cm deep. Several large cornice-triggered avalanches also occurred on Sunday and Monday. One stepped down into lower facet layers producing a crown up to 2 m deep.

Snowpack Summary

Total snowpack depths are approximately 250 cm at treeline. Recent daily new snow amounts have not been particularly high in the last few days, giving the storm snow a chance to settle and gain a little strength. Strong winds have redistributed some of this snow into the classic lee areas in exposed terrain-behind ridgelines, summits and exposed rolls and features. A surface hoar/facet/crust interface from mid-December is well preserved and acting as a persistent weak layer. This is buried 100 to 150 cm deep and has been reactive to natural and human triggers. The increased depth is beginning to make triggering more difficult but bear in mind it also increases the size of anything that does go on this layer, which in turn increases the consequences.

Problems

Wind Slabs

An icon showing Wind Slabs
Strong winds combined with new snow have resulted in widespread wind slabs on lee slopes. I'd be suspect of any open slope, even around treeeline.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 5

Persistent Slabs

An icon showing Persistent Slabs
Surface hoar buried about a metre below the surface has created a dangerous and tricky avalanche problem. It's now fairly hard to trigger this layer but if you do, large avalanches will result. Conservative terrain choices are appropriate.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 7

Cornices

An icon showing Cornices
Anticipated warm alpine temperatures will make cornices unstable. The heavy load of a cornice fall could readily overload one of the weak layers buried in the snowpack causing a large and destructive avalanche.

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

Elevations: Alpine.

Likelihood

Likely

Expected Size

3 - 6

Valid until: Jan 4th, 2012 8:00AM