Avalanche Forecast

Issued: Mar 3rd, 2013 9:33AM

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

pgoddard, Avalanche Canada

Sea To Sky.

Watch out for slopes being warmed by direct sun. This may locally raise the avalanche danger.

Summary

Confidence

Fair - Due to limited field observations

Weather Forecast

Monday: No snow. Mainly sunny. Light winds. Freezing level around 1200 m.Tuesday: Light snow. Light S winds. Freezing level around 1100 m.Wednesday: Light snow. Light S winds. Freezing level around 900 m.

Avalanche Summary

A widespread natural avalanche cycle (with avalanches from size 2-4) occurred on Friday/Saturday in response to intense storm-loading. Numerous large, deep fracture lines can be seen from the Sea-to-Sky corridor. These failed low in the start zone, leaving hangfire (unreleased areas of the slope). Numerous size 1-2 slabs were also triggered by skiers directly, remotely, and sympathetically at and below treeline. These failed on either storm slab weaknesses or buried persistent weak layers.

Snowpack Summary

Strong NW winds redistributed storm snow onto south and east aspects on Sunday. This reverse loading pattern may have left wind slabs in unexpected locations.The recent storm delivered well over 100 mm of precipitation, which fell with warming temperatures, dropping rain below about 1500-1900 m, depending on location. Strong southerly winds during the storm created wind slabs on lee terrain. Numerous weaknesses developed within the storm snow. A weakness of surface hoar and/or a crust exists within the upper snowpack (now 1-2 m deep), which has been reactive over the last week, creating very large avalanches. Direct sunshine may trigger some further shedding of storm snow on Monday. The lower snowpack is well settled.

Problems

Wind Slabs

Strong winds switched direction on Sunday, meaning that wind slabs may be found on many slopes, perhaps in unusual locations.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Give cornices a wide berth when travelling on or below ridges.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 6

Storm Slabs

Recent storm snow will take some time to stabilize. A persistent weak layer, now buried down 1-2 m, could increase the destructive potential of slabs. Sunshine could weaken new snow and cause some more avalanche activity.

Avoid paths that have not avalanched recently.>Be aware of the potential for large, deep avalanches due to the presence of buried weaknesses.>Avoid travelling on slopes which are becoming wet due to warm temperatures or sun.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 6

Valid until: Mar 4th, 2013 2:00PM