Avalanche Forecast

Issued: Mar 29th, 2013 9:29AM

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

jlammers, Avalanche Canada

Northwest Coastal.

Be alert to conditions that change with daytime warming. Danger ratings may exceed posted levels when solar radiation is strong.

Summary

Confidence

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

Weather Forecast

No precipitation is expected for the forecast period. Although high cloud is forecast on Saturday, generally clear skies are expected on Sunday and Monday.Winds will be light from the west on Saturday, generally calm on Sunday, then switching to light and southwesterly Monday.Freezing levels will hover at about 1300m on Saturday, 2400m on Sunday and then 1900m on Monday.

Avalanche Summary

In the far north of the region a cornice collapse triggered a size 3 slab avalanche which failed down to glacier ice. In recent days, solar-triggered natural slab avalanches up to 3.5 have been reported in steep terrain, likely failing on the March 9th layer. Loose wet sluffs up to 2.0 have also been reported. As well, a recent size 2.5 slab avalanche was remotely triggered by a skier in the Hidden Lake area near Shames. Once again, the March 9 surface hoar layer was the culprit. Nobody was caught in the slide.

Snowpack Summary

Surface snow has settled with the influence of warm temperatures and surface hoar is growing on shaded slopes. Solar aspects and lower elevation terrain are now well into a daily melt-freeze cycle. Wind slabs may be found at alpine and treeline elevations on many aspects due to variable winds.Between 50-75cm below the surface is layer of surface hoar buried on March 9th which is variably reactive. In some areas it is stubborn and requires a significant trigger, while in other areas the layer is well preserved and primed for human triggering with the potential for very large avalanches. Check out the Forecaster's Blog for related discussion.The mid snowpack is generally well settled and strong. Having said that, basal facets may resurface as a concern with spring warming, particularly in the north of the region.Cornices are large and untrustworthy, especially when the sun is out.

Problems

Persistent Slabs

In some areas the March 9th layer can be triggered from a distance, propagate across large distances and create surprisingly large avalanches.

Be aware of the potential for large avalanches due to the presence of buried surface hoar.>Choose well supported terrain without convexities.>Avoid areas with overhead hazard.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 6

Loose Wet

Expect loose wet sluffs to fail on sun-exposed slopes.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

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

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Cornices

Large developed cornices loom over slopes. Forecast warming will increase the chances of failure with the potential to initiate large avalanches.

Give cornices a wide berth when travelling on or below ridges.>Pay attention to overhead hazards like cornices.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 6

Valid until: Mar 30th, 2013 2:00PM