Avalanche Forecast

Issued: Mar 18th, 2013 10:42AM

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

pgoddard, Avalanche Canada

Purcells.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Tuesday

Weather Forecast

Monday night: Light snow. Moderate NW winds. Alpine temperature near -15.Tuesday: No snow. Sunshine. Moderate SW winds. Alpine temperature near -10.Wednesday: Moderate to heavy snow (15-25 cm). Strong to extreme SW winds. Alpine temperature near -4.Thursday: Light snow. Light SW winds. Alpine temperature near -10.

Avalanche Summary

On Monday, skiers triggered several small soft slabs and sluffs on wind-loaded or steep terrain. On Sunday, a natural cycle to size 2.5 was observed in the Bugaboos on a variety of aspects in the alpine.

Snowpack Summary

New snow was shifted into reactive slabs by strong SW-NE winds on Monday. Deep and cohesive storm slabs which formed last week are slowly gaining strength, but are not yet fully settled. A weak layer of surface hoar and/or a crust sits about 50-120 cm below the surface. It’s of most concern in the alpine. (At low elevations, it’s likely to be difficult to trigger underneath a supportive crust). This layer will probably linger, with ‘low probability/ high consequence’ type character. A facet/crust layer sits at the base of the snowpack in some places.

Problems

Wind Slabs

Touchy wind slabs may be lurking behind ridges and ribs on a variety of slopes.

Avoid freshly wind loaded features.>Give cornices a wide berth when travelling on or below ridges.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Loose Wet

Be wary of travelling on or below steep slopes which are being warmed by direct sun. Storm snow may fail naturally with the influence of solar radiation.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Pay attention to overhead hazards.>

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

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

A weakness buried up to 120 cm deep may still be within the realms of triggering, especially with a very heavy load, from a thin-spot trigger point and/or at high elevations.

Be aware of the potential for large, deep avalanches due to the presence of buried weaknesses.>Be aware of thin areas that may propagate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 6

Valid until: Mar 19th, 2013 2:00PM