Avalanche Forecast

Issued: Dec 30th, 2014 8:01AM

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

danyelle magnan, Parks Canada

Glacier.

http://www.pc.gc.ca/apps/links/goto_e.asp?destination=http://www.facebook.com/MRGnationalparks/posts/608542575941919Touchy windslabs and persistent slabs exist in many areas. Although the clues of instability, such as whumphing, are becoming less obvious the potential for large avalanches will persist. Stay vigilant and be cautious in your terrain selection.

Summary

Weather Forecast

A ridge of high pressure will keep things clear and cold through Thursday. Today alpine temps should be slightly inverted with a high of -12, while valley bottom temps will stay around -17. Winds will become light at treeline and moderate at ridgetop today. Wednesday will be similar but slightly warmer. Thursday will become cloudy with flurries.

Snowpack Summary

Cold temps are facetting the upper snow, while N'ly winds are reverse loading slopes and creating windslabs. The Dec 17 surface hoar layer is down ~50-70cm and on top of a thick rain crust up to 2100m. This layer is widespread and highly reactive in many areas. The Dec 9 surface hoar is down ~ 70-90cm but is more spotty in distribution.

Avalanche Summary

Yesterday skiers triggered a size 2 skinning up Youngs Peak. The 1m deep windslab propagated 150m wide and ran 300m. No-one was involved. Over the past week there have been daily reports of rider triggered avalanches to size 2.0 failing on the Dec 17 surface hoar. Many of these have been remotely triggered, and sometimes triggering slopes overhead.

Confidence

Problems

Persistent Slabs

A touchy surface hoar layer continues to be reactive. Avalanches continue to be triggered, even in areas that have been heavily traveled. Some areas offer no clues of instability, but the potential for large avalanches exist.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Wind Slabs

Winds have been steady in the 40-50km/h range from the north for the past 48 hours. With lots of snow available to transport, expect windslabs on lee features. A size 2 windslab was triggered by skiers yesterday (see details tab).

Be cautious as you transition into wind affected terrain.Use caution in lee areas. Recent wind loading have created wind slabs.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Dec 31st, 2014 8:00AM