Avalanche Forecast

Issued: Apr 7th, 2014 9:36AM

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

swerner, Avalanche Canada

South Coast.

Check out the new Forecaster Blog and gain insight of how to manage cornices, and how warming influences the snowpack.

Summary

Confidence

Fair - Intensity of incoming weather systems is uncertain on Tuesday

Weather Forecast

Precipitation and strong SW winds will prevail as the cold front moves across the region Tuesday. Tuesday: Mainly cloudy with snow up to 10 cm. Freezing levels 1900 m then dropping overnight to valley bottom. Ridgetop winds moderate from the SW. Wednesday: A mix of sun and cloud. Ridgetop winds light from the West. Freezing levels near 1300 m. Thursday: Mainly cloudy and some flurries expected. Ridgetop winds light from the West. Freezing levels near 1300 m.

Avalanche Summary

Small loose dry avalanches were seen from steep rocky terrain features. Loose wet avalanches were also seen on solar aspects. I suspect natural activity will continue with the warmer temperatures and insignificant overnight re-freeze. Smaller surface avalanches may trigger deeper weak layers, especially in thinner snowpack areas.

Snowpack Summary

Up to 20 cm of new snow sits above a mix of surface hoar, facets and melt freeze crusts. The new snow seems to have a poor bond to old surfaces and isolated wind slabs likely exist. Warmer temperatures and rising freezing levels will likely weaken the snow surfaces and become moist or wet.Recent warm temperatures have helped to settle and strengthen the upper snowpack and snowpack tests have been producing hard resistant planar shears on the late March crust down 30-50 cm.The persistent weak layers from early March and early February continue to be a concern. The March melt-freeze crust/surface hoar is reported to be down 60 - 100cm. The February crust/facet/surface hoar layer is now deeply buried down 150 - 250cm. These layers are mostly inactive at this time, but could re-awaken with extended warming, solar influence and precipitation through the forecast period.

Problems

Wind Slabs

Strong SW winds have set up wind slab problems on leeward slopes, behind ridge crests and mid slope features like ribs/rock outcroppings. Sagging cornices may become weak with warming and solar radiation.

Give cornices a wide berth when travelling on or below ridges.>Use ridges or ribs to avoid pockets of wind loaded snow.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Deep Persistent Slabs

Three buried weak layers exist in the snowpack. Deep releases have become rare; however, the weak layers could be activated by cornice fall, a surface avalanche in motion, or intense loading from snow, and wind.

Be aware of thin areas that may propogate to deeper instabilites.>Be aware of the potential for large, deep avalanches due to the presence of buried facets and surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 7

Loose Wet

With warmer temperatures, limited overnight re-freeze and rain forecast, loose wet avalanches are likely.

Avoid slopes when temperatures rise and the surface snow becomes moist or wet. Signs of instability are pinwheels and natural avalanches. >Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Valid until: Apr 8th, 2014 2:00PM