Avalanche Forecast

Issued: Apr 2nd, 2013 9:33AM

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

pmarshall, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Fair

Weather Forecast

Synopsis: The upper ridge of high pressure rebuilds on Wednesday resulting in more sun through Thursday morning. The ridge gives way to a low pressure system later on Thursday bringing moderate precipitation and increasing winds. Wednesday: A mix of sun and cloud. The freezing level is around 1200 m and winds are light from the southwest.Thursday: Increasing cloud with light snow developing in the evening. The freezing level rises to 1400 m during the day and winds are generally light from the south. Friday: Moderate precipitation. The freezing level is near 1000 m.

Avalanche Summary

In recent days loose wet activity to size 2 has been observed in steeper sun-exposed terrain. Natural cornice releases to size 3 were also noted. A size 1.5 slab avalanche was also remotely triggered from 75m away. I would suspect the March 9th interface was the culprit with this event.

Snowpack Summary

Surface snow has settled with the influence of warm temperatures and surface faceting continues on steep shaded slopes. Solar aspects in the alpine and all 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. In other areas the layer is still well preserved showing sudden planar or sudden collapse test results, and remains a primary concern among some professional operators.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

Reports of remote triggering suggest the March 9th surface hoar layer is still touchy in some areas. Where it is still reactive, avalanches can be large and potentially destructive.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 5

Loose Wet

Loose wet avalanches are likely on steep south facing slopes during the day if the sun is shining.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

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

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Cornices

Large developed cornices loom over slopes. A cornice fall has the potential to initiate large avalanches.

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

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 6

Valid until: Apr 3rd, 2013 2:00PM