Avalanche Forecast

Issued: Mar 13th, 2012 10:46AM

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.

jfloyer, Avalanche Canada

Kootenay Boundary.

Another storm arrives late in the day on Wednesday. Sick of seeing red? Check the forecaster blog!

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Wednesday: A Pacific Frontal system arriving in the afternoon will bring around 10-15cm new snow with continued strong SW winds. Freezing levels will be around 1000m. On Thursday, a stronger pulse of precipitation will bring 10-20cm new snow, again with strong SW winds. Freezing levels will go up to around 1500m. On Friday, precipitation will continue but should become lighter. Freezing level again around 1500m.

Avalanche Summary

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

Approximately 25 cm new snow fell on top of previous storm amounts from Friday night and Saturday night. This has added to the snow amounts overlying a 2 - 6mm surface hoar on north aspects and a 2cm sun crust on solar aspects. Moist snow was found Friday to 1800m, I suspect there was little change Saturday. The leap year SH is now down around 40 - 50 cm and is failing as a resistant planar shear in snowpack tests. The early February surface hoar is down 80 - 140cm, snowpack tests show moderate to hard forces generating sudden planar shears on this layer.

Problems

Wind Slabs

Mostly S and SW winds, however, recent reverse-loading has occurred in response to E winds. Expect wind slabs to be fat, touchy and windspread.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 5

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

If forecast heavy amounts of new snow come through, storm slabs may overload buried weaknesses & could even step down, producing large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Valid until: Mar 14th, 2012 9:00AM