Avalanche Forecast

Issued: Mar 15th, 2012 4:00PM

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

Avalanche Canada jfloyer, Avalanche Canada

Continued storms as well as solar warming will maintain elevated avalanche danger through the weekend. Read the forecaster blog about message fatigue and BE CAREFUL OUT THERE.

Summary

Confidence

Poor - Timing or intensity of solar radiation is uncertain

Weather Forecast

5-10 cm new snow is expected to fall Thursday night with SW winds blowing to 60 km/h. On Friday, unsettled air moves in behind the most recent storm system, which will generally bring only light amounts, but could locally produce heavier snowfall. Sunny breaks are also possible between the flurries/snowfall. Freezing level is expected to be around 1500m, winds SW around 30 km/h. On Saturday, a system pushes through the region bring 10-15 cm new snow. As with Friday, sunny breaks are also possible. Freezing levels should remain around 1500 m, winds around 40 km/h from the south, which may become gustier in the afternoon. On Sunday, flurries are likely, as are significant sunny breaks. The winds should become light or calm.

Avalanche Summary

On Wednesday, ski cutting and explosive testing produced avalanches up to size 2.5 on a variety of aspects. Just to the north of the region, a vehicle triggered a size 2.5 avalanche in the recent storm snow. On Tuesday, several large (size 2.5) fracture lines in commonly skied areas at Kootenay Pass were observed following an intense wind event. On Monday, natural avalanches up to size 2 occurred in response to storm snow loading; ski-cutting to size 1.5 was also reported. This activity continues a very active period of avalanche activity that has been ongoing since early March.

Snowpack Summary

Good dumps of new snow are adding to recent storm slabs of around 40-60 cm, which overly a variety of surfaces including old wind slabs in exposed areas, a sun crust on southern aspects or even (spotty reports) a 2 - 6mm surface hoar on north and east aspects. Prior to that, recent most snow fell to around 1800m. The leap year SH is now down around 40 - 50 cm and is failing as a resistant planar shear in snowpack tests. The more significant early February surface hoar is down 80 - 140cm, snowpack tests show moderate to hard forces generating sudden planar shears on this layer. Below the early February surface hoar layer, the snowpack is strong in most places. Cornices are growing and would act as a significant trigger for all the layers mentioned above if they drop.

Problems

Wind Slabs

An icon showing Wind Slabs
Fresh wind slabs are forming on mostly north to east aspects in response to new snow and loading by SW winds. Old wind slabs are now buried but could enhance the size of potential releases on a variety of aspects in exposed areas.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Persistent Slabs

An icon showing Persistent Slabs
The deep nature of the mid-February surface hoar layer makes potential avalanches triggered on this layer large and destructive. Regular and ongoing avalanche activity associated with this layer indicates it is very much still alive.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

3 - 7

Storm Slabs

An icon showing Storm Slabs
Heavy amounts of new snow are overloading buried weaknesses and could step down, producing large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

2 - 6

Valid until: Mar 16th, 2012 9:00AM