Avalanche Forecast

Issued: Mar 30th, 2013 3:00PM

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

Good

Weather Forecast

Clear skies are expected on Sunday with increased cloud on Monday and a chance of light precipitation on Tuesday. Winds will be mostly light from the southwest increasing to moderate late Monday. Freezing levels may reach 2400m on Sunday, 1800m on Monday and then 1400m on Tuesday.

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, natural slab avalanches up to 2.5 have been reported, likely failing on the March 9th layer. Several loose wet sluffs up to size 2.5 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. On Friday a skier-triggered size 1 slab occurred on a solar aspect on March 9th surface hoar. This avalanche remotely triggered a 2nd slab (150m away) lower down in a similar terrain feature again on the March 9th layer.

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 with sun-exposed slopes becoming very weak with daytime warming.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.>Avoid areas with overhead hazard.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 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 - 5

Cornices

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

Cornices become weak with daytime heating, so travel early on exposed slopes.>Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 6

Valid until: Mar 31st, 2013 2:00PM