Avalanche Forecast

Issued: Feb 16th, 2013 9:48AM

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

triley, Avalanche Canada

Purcells.

The last storm was very reactive, and now the new storm is adding to the load above the same weak layer. I suggest conservative goals and a day of watching what happens from safe lines.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Sunday

Weather Forecast

Overnight and Sunday: Snow fall is expected to continue into the night and then taper off by late morning. Expect 10-20 cms total at treeline with moderate West winds and strong gusts during the snow fall. A weak ridge of high pressure is expected to fill in behind the trough, shifting the winds to moderate Northerly with strong gusts.Monday: The weak ridge is expected to flatten out and let the next trough move inland from the coast. Expect mainly cloudy skies and light precipitation with light Westerly winds and the freezing level rising up to about 1000 metres.Tuesday: The next weak trough is expected to bring another pulse of precipitation to the region, combined with light West winds and slightly cooler temperatures.

Avalanche Summary

Some explosives control resulted in small avalanches from large triggers. Otherwise no new avalanches reported.

Snowpack Summary

New snow is adding to the recent storm slab that is between 15-30 cms across the region. This new load is expected to create another cycle of wind slab releases in the alpine and treeline, and may cause the recent storm slab to become more reactive where it is sitting on the weak surface hoar layer that was buried on February 12th. The recent storm slab has also been reactive on Southerly aspects where a sun crust formed during the period from February 8th-11th. Loading on the recent storm may cause another cycle of natural activity, or an increased sensitivity to human triggers. There are older weak layers that are now buried down around 70-80 cms and also at about 110 cms. These layers have been unlikely to trigger by skiers, but they may still be sensitive to large loads like avalanches in motion or cornice fall.

Problems

Storm Slabs

New snow is adding to the load on the recent storm slab, this slab may be easy to trigger where it is sitting on a layer of buried surface hoar and/or a sun crust.

The new snow will require several days to settle and stabilize.>Good day to make conservative terrain choices.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Wind Slabs

New wind slabs are expected to develop overnight due to forecast snow and moderate gusty West winds. Recent wind slabs may not be well bonded.

Avoid freshly wind loaded features.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

There are a couple of older layers of buried surface hoar and crust combinations that are buried down about 70 cms and 100 cms, that may be triggered by large additional loads.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 6

Valid until: Feb 17th, 2013 2:00PM